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| author | Arnold D. Robbins <arnold@skeeve.com> | 2014-03-27 20:58:06 +0200 |
|---|---|---|
| committer | Arnold D. Robbins <arnold@skeeve.com> | 2014-03-27 20:58:06 +0200 |
| commit | 82da42cf14d16813bca40431e86dc78b2ca6d7f5 (patch) | |
| tree | 0efc5deaaebe2ccd2e6c0b239b2fcc0289e5203b | |
| parent | 3355ce597d39925ea1221c92f62ef8dcb80d7274 (diff) | |
| download | gawk-82da42cf14d16813bca40431e86dc78b2ca6d7f5.tar.gz | |
BBS-list examples redone. Yay! Thanks to Antonio.
| -rw-r--r-- | doc/ChangeLog | 5 | ||||
| -rw-r--r-- | doc/gawk.info | 1658 | ||||
| -rw-r--r-- | doc/gawk.texi | 508 | ||||
| -rw-r--r-- | doc/gawktexi.in | 508 |
4 files changed, 1353 insertions, 1326 deletions
diff --git a/doc/ChangeLog b/doc/ChangeLog index 15e6d958..fed2cc82 100644 --- a/doc/ChangeLog +++ b/doc/ChangeLog @@ -1,3 +1,8 @@ +2014-03-27 Antonio Giovanni Colombo <azc100@gmail.com> + + * gawktexi.in: Redo all the examples using BBS-list to a different + file that doesn't use out-of-date concepts. + 2014-03-10 Arnold D. Robbins <arnold@skeeve.com> * gawktexi.in: Finish indexing improvements. (For now, anyway.) diff --git a/doc/gawk.info b/doc/gawk.info index a275d9c2..2e18da5b 100644 --- a/doc/gawk.info +++ b/doc/gawk.info @@ -1767,30 +1767,30 @@ File: gawk.info, Node: Sample Data Files, Next: Very Simple, Prev: Running ga =============================== Many of the examples in this Info file take their input from two sample -data files. The first, `BBS-list', represents a list of computer -bulletin board systems together with information about those systems. +data files. The first, `mail-list', represents a list of peoples' names +together with their email addresses and information about those people. The second data file, called `inventory-shipped', contains information about monthly shipments. In both files, each line is considered to be one "record". - In the data file `BBS-list', each record contains the name of a -computer bulletin board, its phone number, the board's baud rate(s), -and a code for the number of hours it is operational. An `A' in the -last column means the board operates 24 hours a day. A `B' in the last -column means the board only operates on evening and weekend hours. A -`C' means the board operates only on weekends: - - aardvark 555-5553 1200/300 B - alpo-net 555-3412 2400/1200/300 A - barfly 555-7685 1200/300 A - bites 555-1675 2400/1200/300 A - camelot 555-0542 300 C - core 555-2912 1200/300 C - fooey 555-1234 2400/1200/300 B - foot 555-6699 1200/300 B - macfoo 555-6480 1200/300 A - sdace 555-3430 2400/1200/300 A - sabafoo 555-2127 1200/300 C + In the data file `mail-list', each record contains the name of a +person, his/her phone number, his/her email-address, and a code for +their relationship with the author of the list. An `A' in the last +column means that the person is an acquaintance. An `F' in the last +column means that the person is a friend. An `R' means that the person +is a relative: + + Amelia 555-5553 amelia.zodiacusque@gmail.com F + Anthony 555-3412 anthony.asserturo@hotmail.com A + Becky 555-7685 becky.algebrarum@gmail.com A + Bill 555-1675 bill.drowning@hotmail.com A + Broderick 555-0542 broderick.aliquotiens@yahoo.com R + Camilla 555-2912 camilla.infusarum@skynet.be R + Fabius 555-1234 fabius.undevicesimus@ucb.edu F + Julie 555-6699 julie.perscrutabor@skeeve.com F + Martin 555-6480 martin.codicibus@hotmail.com A + Samuel 555-3430 samuel.lanceolis@shu.edu A + Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R The data file `inventory-shipped' represents information about shipments during the year. Each record contains the month, the number @@ -1827,32 +1827,32 @@ File: gawk.info, Node: Very Simple, Next: Two Rules, Prev: Sample Data Files, ======================== The following command runs a simple `awk' program that searches the -input file `BBS-list' for the character string `foo' (a grouping of +input file `mail-list' for the character string `li' (a grouping of characters is usually called a "string"; the term "string" is based on similar usage in English, such as "a string of pearls," or "a string of cars in a train"): - awk '/foo/ { print $0 }' BBS-list + awk '/li/ { print $0 }' mail-list -When lines containing `foo' are found, they are printed because +When lines containing `li' are found, they are printed because `print $0' means print the current line. (Just `print' by itself means the same thing, so we could have written that instead.) - You will notice that slashes (`/') surround the string `foo' in the -`awk' program. The slashes indicate that `foo' is the pattern to -search for. This type of pattern is called a "regular expression", -which is covered in more detail later (*note Regexp::). The pattern is -allowed to match parts of words. There are single quotes around the -`awk' program so that the shell won't interpret any of it as special -shell characters. + You will notice that slashes (`/') surround the string `li' in the +`awk' program. The slashes indicate that `li' is the pattern to search +for. This type of pattern is called a "regular expression", which is +covered in more detail later (*note Regexp::). The pattern is allowed +to match parts of words. There are single quotes around the `awk' +program so that the shell won't interpret any of it as special shell +characters. Here is what this program prints: - $ awk '/foo/ { print $0 }' BBS-list - -| fooey 555-1234 2400/1200/300 B - -| foot 555-6699 1200/300 B - -| macfoo 555-6480 1200/300 A - -| sabafoo 555-2127 1200/300 C + $ awk '/li/ { print $0 }' mail-list + -| Amelia 555-5553 amelia.zodiacusque@gmail.com F + -| Broderick 555-0542 broderick.aliquotiens@yahoo.com R + -| Julie 555-6699 julie.perscrutabor@skeeve.com F + -| Samuel 555-3430 samuel.lanceolis@shu.edu A In an `awk' rule, either the pattern or the action can be omitted, but not both. If the pattern is omitted, then the action is performed @@ -1861,7 +1861,7 @@ is to print all lines that match the pattern. Thus, we could leave out the action (the `print' statement and the curly braces) in the previous example and the result would be the same: -`awk' prints all lines matching the pattern `foo'. By comparison, +`awk' prints all lines matching the pattern `li'. By comparison, omitting the `print' statement but retaining the curly braces makes an empty action that does nothing (i.e., no lines are printed). @@ -1967,25 +1967,19 @@ the string `21'. If a line contains both strings, it is printed twice, once by each rule. This is what happens if we run this program on our two sample data -files, `BBS-list' and `inventory-shipped': +files, `mail-list' and `inventory-shipped': $ awk '/12/ { print $0 } - > /21/ { print $0 }' BBS-list inventory-shipped - -| aardvark 555-5553 1200/300 B - -| alpo-net 555-3412 2400/1200/300 A - -| barfly 555-7685 1200/300 A - -| bites 555-1675 2400/1200/300 A - -| core 555-2912 1200/300 C - -| fooey 555-1234 2400/1200/300 B - -| foot 555-6699 1200/300 B - -| macfoo 555-6480 1200/300 A - -| sdace 555-3430 2400/1200/300 A - -| sabafoo 555-2127 1200/300 C - -| sabafoo 555-2127 1200/300 C + > /21/ { print $0 }' mail-list inventory-shipped + -| Anthony 555-3412 anthony.asserturo@hotmail.com A + -| Camilla 555-2912 camilla.infusarum@skynet.be R + -| Fabius 555-1234 fabius.undevicesimus@ucb.edu F + -| Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R + -| Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R -| Jan 21 36 64 620 -| Apr 21 70 74 514 -Note how the line beginning with `sabafoo' in `BBS-list' was printed +Note how the line beginning with `Jean-Paul' in `mail-list' was printed twice, once for each rule. @@ -2061,7 +2055,7 @@ Most often, each line in an `awk' program is a separate statement or separate rule, like this: awk '/12/ { print $0 } - /21/ { print $0 }' BBS-list inventory-shipped + /21/ { print $0 }' mail-list inventory-shipped However, `gawk' ignores newlines after any of the following symbols and keywords: @@ -3106,14 +3100,14 @@ A regular expression can be used as a pattern by enclosing it in slashes. Then the regular expression is tested against the entire text of each record. (Normally, it only needs to match some part of the text in order to succeed.) For example, the following prints the -second field of each record that contains the string `foo' anywhere in +second field of each record that contains the string `li' anywhere in it: - $ awk '/foo/ { print $2 }' BBS-list - -| 555-1234 + $ awk '/li/ { print $2 }' mail-list + -| 555-5553 + -| 555-0542 -| 555-6699 - -| 555-6480 - -| 555-2127 + -| 555-3430 Regular expressions can also be used in matching expressions. These expressions allow you to specify the string to match against; it need @@ -3921,67 +3915,82 @@ processed, so that the very first record is read with the proper separator. To do this, use the special `BEGIN' pattern (*note BEGIN/END::). For example: - awk 'BEGIN { RS = "/" } - { print $0 }' BBS-list - -changes the value of `RS' to `"/"', before reading any input. This is -a string whose first character is a slash; as a result, records are -separated by slashes. Then the input file is read, and the second rule -in the `awk' program (the action with no pattern) prints each record. -Because each `print' statement adds a newline at the end of its output, -this `awk' program copies the input with each slash changed to a -newline. Here are the results of running the program on `BBS-list': - - $ awk 'BEGIN { RS = "/" } - > { print $0 }' BBS-list - -| aardvark 555-5553 1200 - -| 300 B - -| alpo-net 555-3412 2400 - -| 1200 - -| 300 A - -| barfly 555-7685 1200 - -| 300 A - -| bites 555-1675 2400 - -| 1200 - -| 300 A - -| camelot 555-0542 300 C - -| core 555-2912 1200 - -| 300 C - -| fooey 555-1234 2400 - -| 1200 - -| 300 B - -| foot 555-6699 1200 - -| 300 B - -| macfoo 555-6480 1200 - -| 300 A - -| sdace 555-3430 2400 - -| 1200 - -| 300 A - -| sabafoo 555-2127 1200 - -| 300 C + awk 'BEGIN { RS = "u" } + { print $0 }' mail-list + +changes the value of `RS' to `u', before reading any input. This is a +string whose first character is the letter "u;" as a result, records +are separated by the letter "u." Then the input file is read, and the +second rule in the `awk' program (the action with no pattern) prints +each record. Because each `print' statement adds a newline at the end +of its output, this `awk' program copies the input with each `u' +changed to a newline. Here are the results of running the program on +`mail-list': + + $ awk 'BEGIN { RS = "u" } + > { print $0 }' mail-list + -| Amelia 555-5553 amelia.zodiac + -| sq + -| e@gmail.com F + -| Anthony 555-3412 anthony.assert + -| ro@hotmail.com A + -| Becky 555-7685 becky.algebrar + -| m@gmail.com A + -| Bill 555-1675 bill.drowning@hotmail.com A + -| Broderick 555-0542 broderick.aliq + -| otiens@yahoo.com R + -| Camilla 555-2912 camilla.inf + -| sar + -| m@skynet.be R + -| Fabi + -| s 555-1234 fabi + -| s. + -| ndevicesim + -| s@ + -| cb.ed + -| F + -| J + -| lie 555-6699 j + -| lie.perscr + -| tabor@skeeve.com F + -| Martin 555-6480 martin.codicib + -| s@hotmail.com A + -| Sam + -| el 555-3430 sam + -| el.lanceolis@sh + -| .ed + -| A + -| Jean-Pa + -| l 555-2127 jeanpa + -| l.campanor + -| m@ny + -| .ed + -| R -| -Note that the entry for the `camelot' BBS is not split. In the -original data file (*note Sample Data Files::), the line looks like -this: +Note that the entry for the name `Bill' is not split. In the original +data file (*note Sample Data Files::), the line looks like this: - camelot 555-0542 300 C + Bill 555-1675 bill.drowning@hotmail.com A -It has one baud rate only, so there are no slashes in the record, -unlike the others which have two or more baud rates. In fact, this -record is treated as part of the record for the `core' BBS; the newline +It contains no `u' so there is no reason to split the record, unlike +the others which have one or more occurrences of the `u'. In fact, +this record is treated as part of the previous record; the newline separating them in the output is the original newline in the data file, not the one added by `awk' when it printed the record! Another way to change the record separator is on the command line, using the variable-assignment feature (*note Other Arguments::): - awk '{ print $0 }' RS="/" BBS-list + awk '{ print $0 }' RS="u" mail-list -This sets `RS' to `/' before processing `BBS-list'. +This sets `RS' to `u' before processing `mail-list'. - Using an unusual character such as `/' for the record separator -produces correct behavior in the vast majority of cases. + Using an alphabetic character such as `u' for the record separator +is highly likely to produce strange results. Using an unusual +character such as `/' is more likely to produce correct behavior in the +majority of cases, but there are no guarantees. The moral is: Know Your +Data. There is one unusual case, that occurs when `gawk' is being fully POSIX-compliant (*note Options::). Then, the following (extreme) @@ -4150,26 +4159,24 @@ get the empty string. (If used in a numeric operation, you get zero.) field, is a special case: it represents the whole input record when you are not interested in specific fields. Here are some more examples: - $ awk '$1 ~ /foo/ { print $0 }' BBS-list - -| fooey 555-1234 2400/1200/300 B - -| foot 555-6699 1200/300 B - -| macfoo 555-6480 1200/300 A - -| sabafoo 555-2127 1200/300 C + $ awk '$1 ~ /li/ { print $0 }' mail-list + -| Amelia 555-5553 amelia.zodiacusque@gmail.com F + -| Julie 555-6699 julie.perscrutabor@skeeve.com F -This example prints each record in the file `BBS-list' whose first -field contains the string `foo'. The operator `~' is called a -"matching operator" (*note Regexp Usage::); it tests whether a string -(here, the field `$1') matches a given regular expression. +This example prints each record in the file `mail-list' whose first +field contains the string `li'. The operator `~' is called a "matching +operator" (*note Regexp Usage::); it tests whether a string (here, the +field `$1') matches a given regular expression. - By contrast, the following example looks for `foo' in _the entire + By contrast, the following example looks for `li' in _the entire record_ and prints the first field and the last field for each matching input record: - $ awk '/foo/ { print $1, $NF }' BBS-list - -| fooey B - -| foot B - -| macfoo A - -| sabafoo C + $ awk '/li/ { print $1, $NF }' mail-list + -| Amelia F + -| Broderick R + -| Julie F + -| Samuel A ---------- Footnotes ---------- @@ -4197,16 +4204,16 @@ For the twentieth record, field number 20 is printed; most likely, the record has fewer than 20 fields, so this prints a blank line. Here is another example of using expressions as field numbers: - awk '{ print $(2*2) }' BBS-list + awk '{ print $(2*2) }' mail-list `awk' evaluates the expression `(2*2)' and uses its value as the number of the field to print. The `*' sign represents multiplication, so the expression `2*2' evaluates to four. The parentheses are used so that the multiplication is done before the `$' operation; they are necessary whenever there is a binary operator in the field-number -expression. This example, then, prints the hours of operation (the -fourth field) for every line of the file `BBS-list'. (All of the `awk' -operators are listed, in order of decreasing precedence, in *note +expression. This example, then, prints the type of relationship (the +fourth field) for every line of the file `mail-list'. (All of the +`awk' operators are listed, in order of decreasing precedence, in *note Precedence::.) If the field number you compute is zero, you get the entire record. @@ -4603,53 +4610,46 @@ type `-F\t' at the shell, without any quotes, the `\' gets deleted, so TABs and not `t's. Use `-v FS="t"' or `-F"[t]"' on the command line if you really do want to separate your fields with `t's. - As an example, let's use an `awk' program file called `baud.awk' -that contains the pattern `/300/' and the action `print $1': + As an example, let's use an `awk' program file called `edu.awk' that +contains the pattern `/edu/' and the action `print $1': - /300/ { print $1 } + /edu/ { print $1 } Let's also set `FS' to be the `-' character and run the program on -the file `BBS-list'. The following command prints a list of the names -of the bulletin boards that operate at 300 baud and the first three +the file `mail-list'. The following command prints a list of the names +of the people that work at or attend a university, and the first three digits of their phone numbers: - $ awk -F- -f baud.awk BBS-list - -| aardvark 555 - -| alpo - -| barfly 555 - -| bites 555 - -| camelot 555 - -| core 555 - -| fooey 555 - -| foot 555 - -| macfoo 555 - -| sdace 555 - -| sabafoo 555 - -Note the second line of output. The second line in the original file + $ awk -F- -f edu.awk mail-list + -| Fabius 555 + -| Samuel 555 + -| Jean + +Note the third line of output. The third line in the original file looked like this: - alpo-net 555-3412 2400/1200/300 A + Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R - The `-' as part of the system's name was used as the field + The `-' as part of the person's name was used as the field separator, instead of the `-' in the phone number that was originally intended. This demonstrates why you have to be careful in choosing your field and record separators. Perhaps the most common use of a single character as the field separator occurs when processing the Unix system password file. On -many Unix systems, each user has a separate entry in the system password -file, one line per user. The information in these lines is separated -by colons. The first field is the user's login name and the second is -the user's (encrypted or shadow) password. A password file entry might -look like this: +many Unix systems, each user has a separate entry in the system +password file, one line per user. The information in these lines is +separated by colons. The first field is the user's login name and the +second is the user's encrypted or shadow password. (A shadow password +is indicated by the presence of a single `x' in the second field.) A +password file entry might look like this: - arnold:xyzzy:2076:10:Arnold Robbins:/home/arnold:/bin/bash + arnold:x:2076:10:Arnold Robbins:/home/arnold:/bin/bash The following program searches the system password file and prints -the entries for users who have no password: +the entries for users whose full name is not indicated: - awk -F: '$2 == ""' /etc/passwd + awk -F: '$5 == ""' /etc/passwd File: gawk.info, Node: Full Line Fields, Next: Field Splitting Summary, Prev: Command Line Field Separator, Up: Field Separators @@ -5835,13 +5835,29 @@ prints the first and second fields of each input record, separated by a semicolon, with a blank line added after each newline: $ awk 'BEGIN { OFS = ";"; ORS = "\n\n" } - > { print $1, $2 }' BBS-list - -| aardvark;555-5553 + > { print $1, $2 }' mail-list + -| Amelia;555-5553 -| - -| alpo-net;555-3412 + -| Anthony;555-3412 + -| + -| Becky;555-7685 + -| + -| Bill;555-1675 + -| + -| Broderick;555-0542 + -| + -| Camilla;555-2912 + -| + -| Fabius;555-1234 + -| + -| Julie;555-6699 + -| + -| Martin;555-6480 + -| + -| Samuel;555-3430 + -| + -| Jean-Paul;555-2127 -| - -| barfly;555-7685 - ... If the value of `ORS' does not contain a newline, the program's output runs together on a single line. @@ -6210,25 +6226,25 @@ File: gawk.info, Node: Printf Examples, Prev: Format Modifiers, Up: Printf The following simple example shows how to use `printf' to make an aligned table: - awk '{ printf "%-10s %s\n", $1, $2 }' BBS-list + awk '{ printf "%-10s %s\n", $1, $2 }' mail-list -This command prints the names of the bulletin boards (`$1') in the file -`BBS-list' as a string of 10 characters that are left-justified. It +This command prints the names of the people (`$1') in the file +`mail-list' as a string of 10 characters that are left-justified. It also prints the phone numbers (`$2') next on the line. This produces an aligned two-column table of names and phone numbers, as shown here: - $ awk '{ printf "%-10s %s\n", $1, $2 }' BBS-list - -| aardvark 555-5553 - -| alpo-net 555-3412 - -| barfly 555-7685 - -| bites 555-1675 - -| camelot 555-0542 - -| core 555-2912 - -| fooey 555-1234 - -| foot 555-6699 - -| macfoo 555-6480 - -| sdace 555-3430 - -| sabafoo 555-2127 + $ awk '{ printf "%-10s %s\n", $1, $2 }' mail-list + -| Amelia 555-5553 + -| Anthony 555-3412 + -| Becky 555-7685 + -| Bill 555-1675 + -| Broderick 555-0542 + -| Camilla 555-2912 + -| Fabius 555-1234 + -| Julie 555-6699 + -| Martin 555-6480 + -| Samuel 555-3430 + -| Jean-Paul 555-2127 In this case, the phone numbers had to be printed as strings because the numbers are separated by a dash. Printing the phone numbers as @@ -6246,14 +6262,14 @@ beginning of the `awk' program: awk 'BEGIN { print "Name Number" print "---- ------" } - { printf "%-10s %s\n", $1, $2 }' BBS-list + { printf "%-10s %s\n", $1, $2 }' mail-list The above example mixes `print' and `printf' statements in the same program. Using just `printf' statements can produce the same results: awk 'BEGIN { printf "%-10s %s\n", "Name", "Number" printf "%-10s %s\n", "----", "------" } - { printf "%-10s %s\n", $1, $2 }' BBS-list + { printf "%-10s %s\n", $1, $2 }' mail-list Printing each column heading with the same format specification used for the column elements ensures that the headings are aligned just like @@ -6265,7 +6281,7 @@ be emphasized by storing it in a variable, like this: awk 'BEGIN { format = "%-10s %s\n" printf format, "Name", "Number" printf format, "----", "------" } - { printf format, $1, $2 }' BBS-list + { printf format, $1, $2 }' mail-list At this point, it would be a worthwhile exercise to use the `printf' statement to line up the headings and table data for the @@ -6305,19 +6321,19 @@ work identically for `printf': the same OUTPUT-FILE do not erase OUTPUT-FILE, but append to it. (This is different from how you use redirections in shell scripts.) If OUTPUT-FILE does not exist, it is created. For example, here - is how an `awk' program can write a list of BBS names to one file - named `name-list', and a list of phone numbers to another file + is how an `awk' program can write a list of peoples' names to one + file named `name-list', and a list of phone numbers to another file named `phone-list': $ awk '{ print $2 > "phone-list" - > print $1 > "name-list" }' BBS-list + > print $1 > "name-list" }' mail-list $ cat phone-list -| 555-5553 -| 555-3412 ... $ cat name-list - -| aardvark - -| alpo-net + -| Amelia + -| Anthony ... Each output file contains one name or number per line. @@ -6338,12 +6354,12 @@ work identically for `printf': The redirection argument COMMAND is actually an `awk' expression. Its value is converted to a string whose contents give the shell command to be run. For example, the following produces two files, - one unsorted list of BBS names, and one list sorted in reverse + one unsorted list of peoples' names, and one list sorted in reverse alphabetical order: awk '{ print $1 > "names.unsorted" command = "sort -r > names.sorted" - print $1 | command }' BBS-list + print $1 | command }' mail-list The unsorted list is written with an ordinary redirection, while the sorted list is written by piping through the `sort' utility. @@ -7073,16 +7089,16 @@ assignment is performed at a time determined by its position among the input file arguments--after the processing of the preceding input file argument. For example: - awk '{ print $n }' n=4 inventory-shipped n=2 BBS-list + awk '{ print $n }' n=4 inventory-shipped n=2 mail-list prints the value of field number `n' for all input records. Before the first file is read, the command line sets the variable `n' equal to four. This causes the fourth field to be printed in lines from `inventory-shipped'. After the first file has finished, but before the second file is started, `n' is set to two, so that the second field is -printed in lines from `BBS-list': +printed in lines from `mail-list': - $ awk '{ print $n }' n=4 inventory-shipped n=2 BBS-list + $ awk '{ print $n }' n=4 inventory-shipped n=2 mail-list -| 15 -| 24 ... @@ -7343,17 +7359,17 @@ a specific operator to represent it. Instead, concatenation is performed by writing expressions next to one another, with no operator. For example: - $ awk '{ print "Field number one: " $1 }' BBS-list - -| Field number one: aardvark - -| Field number one: alpo-net + $ awk '{ print "Field number one: " $1 }' mail-list + -| Field number one: Amelia + -| Field number one: Anthony ... Without the space in the string constant after the `:', the line runs together. For example: - $ awk '{ print "Field number one:" $1 }' BBS-list - -| Field number one:aardvark - -| Field number one:alpo-net + $ awk '{ print "Field number one:" $1 }' mail-list + -| Field number one:Amelia + -| Field number one:Anthony ... Because string concatenation does not have an explicit operator, it @@ -7999,9 +8015,9 @@ Boolean operators are: `BOOLEAN1 && BOOLEAN2' True if both BOOLEAN1 and BOOLEAN2 are true. For example, the following statement prints the current input record if it contains - both `2400' and `foo': + both `edu' and `li': - if ($0 ~ /2400/ && $0 ~ /foo/) print + if ($0 ~ /edu/ && $0 ~ /li/) print The subexpression BOOLEAN2 is evaluated only if BOOLEAN1 is true. This can make a difference when BOOLEAN2 contains expressions that @@ -8012,9 +8028,9 @@ Boolean operators are: `BOOLEAN1 || BOOLEAN2' True if at least one of BOOLEAN1 or BOOLEAN2 is true. For example, the following statement prints all records in the input - that contain _either_ `2400' or `foo' or both: + that contain _either_ `edu' or `li' or both: - if ($0 ~ /2400/ || $0 ~ /foo/) print + if ($0 ~ /edu/ || $0 ~ /li/) print The subexpression BOOLEAN2 is evaluated only if BOOLEAN1 is false. This can make a difference when BOOLEAN2 contains expressions that @@ -8434,56 +8450,53 @@ operand is either a constant regular expression enclosed in slashes (`/REGEXP/'), or any expression whose string value is used as a dynamic regular expression (*note Computed Regexps::). The following example prints the second field of each input record whose first field is -precisely `foo': +precisely `li': - $ awk '$1 == "foo" { print $2 }' BBS-list + $ awk '$1 == "li" { print $2 }' mail-list -(There is no output, because there is no BBS site with the exact name -`foo'.) Contrast this with the following regular expression match, -which accepts any record with a first field that contains `foo': +(There is no output, because there is no person with the exact name +`li'.) Contrast this with the following regular expression match, which +accepts any record with a first field that contains `li': - $ awk '$1 ~ /foo/ { print $2 }' BBS-list - -| 555-1234 + $ awk '$1 ~ /foo/ { print $2 }' mail-list + -| 555-5553 -| 555-6699 - -| 555-6480 - -| 555-2127 A regexp constant as a pattern is also a special case of an -expression pattern. The expression `/foo/' has the value one if `foo' -appears in the current input record. Thus, as a pattern, `/foo/' -matches any record containing `foo'. +expression pattern. The expression `/li/' has the value one if `li' +appears in the current input record. Thus, as a pattern, `/li/' matches +any record containing `li'. Boolean expressions are also commonly used as patterns. Whether the pattern matches an input record depends on whether its subexpressions match. For example, the following command prints all the records in -`BBS-list' that contain both `2400' and `foo': - - $ awk '/2400/ && /foo/' BBS-list - -| fooey 555-1234 2400/1200/300 B - - The following command prints all records in `BBS-list' that contain -_either_ `2400' or `foo' (or both, of course): - - $ awk '/2400/ || /foo/' BBS-list - -| alpo-net 555-3412 2400/1200/300 A - -| bites 555-1675 2400/1200/300 A - -| fooey 555-1234 2400/1200/300 B - -| foot 555-6699 1200/300 B - -| macfoo 555-6480 1200/300 A - -| sdace 555-3430 2400/1200/300 A - -| sabafoo 555-2127 1200/300 C - - The following command prints all records in `BBS-list' that do _not_ -contain the string `foo': - - $ awk '! /foo/' BBS-list - -| aardvark 555-5553 1200/300 B - -| alpo-net 555-3412 2400/1200/300 A - -| barfly 555-7685 1200/300 A - -| bites 555-1675 2400/1200/300 A - -| camelot 555-0542 300 C - -| core 555-2912 1200/300 C - -| sdace 555-3430 2400/1200/300 A +`mail-list' that contain both `edu' and `li': + + $ awk '/edu/ && /li/' mail-list + -| Samuel 555-3430 samuel.lanceolis@shu.edu A + + The following command prints all records in `mail-list' that contain +_either_ `edu' or `li' (or both, of course): + + $ awk '/edu/ || /li/' mail-list + -| Amelia 555-5553 amelia.zodiacusque@gmail.com F + -| Broderick 555-0542 broderick.aliquotiens@yahoo.com R + -| Fabius 555-1234 fabius.undevicesimus@ucb.edu F + -| Julie 555-6699 julie.perscrutabor@skeeve.com F + -| Samuel 555-3430 samuel.lanceolis@shu.edu A + -| Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R + + The following command prints all records in `mail-list' that do +_not_ contain the string `li': + + $ awk '! /li/' mail-list + -| Anthony 555-3412 anthony.asserturo@hotmail.com A + -| Becky 555-7685 becky.algebrarum@gmail.com A + -| Bill 555-1675 bill.drowning@hotmail.com A + -| Camilla 555-2912 camilla.infusarum@skynet.be R + -| Fabius 555-1234 fabius.undevicesimus@ucb.edu F + -| Martin 555-6480 martin.codicibus@hotmail.com A + -| Jean-Paul 555-2127 jeanpaul.campanorum@nyu.edu R The subexpressions of a Boolean operator in a pattern can be constant regular expressions, comparisons, or any other `awk' @@ -8594,19 +8607,19 @@ read. Likewise, an `END' rule is executed once only, after all the input is read. For example: $ awk ' - > BEGIN { print "Analysis of \"foo\"" } - > /foo/ { ++n } - > END { print "\"foo\" appears", n, "times." }' BBS-list - -| Analysis of "foo" - -| "foo" appears 4 times. - - This program finds the number of records in the input file `BBS-list' -that contain the string `foo'. The `BEGIN' rule prints a title for the -report. There is no need to use the `BEGIN' rule to initialize the -counter `n' to zero, since `awk' does this automatically (*note -Variables::). The second rule increments the variable `n' every time a -record containing the pattern `foo' is read. The `END' rule prints the -value of `n' at the end of the run. + > BEGIN { print "Analysis of \"li\"" } + > /li/ { ++n } + > END { print "\"li\" appears in", n, "records." }' mail-list + -| Analysis of "li" + -| "li" appears in 4 records. + + This program finds the number of records in the input file +`mail-list' that contain the string `li'. The `BEGIN' rule prints a +title for the report. There is no need to use the `BEGIN' rule to +initialize the counter `n' to zero, since `awk' does this automatically +(*note Variables::). The second rule increments the variable `n' every +time a record containing the pattern `li' is read. The `END' rule +prints the value of `n' at the end of the run. The special patterns `BEGIN' and `END' cannot be used in ranges or with Boolean operators (indeed, they cannot be used with any operators). @@ -8757,7 +8770,7 @@ File: gawk.info, Node: Empty, Prev: BEGINFILE/ENDFILE, Up: Pattern Overview An empty (i.e., nonexistent) pattern is considered to match _every_ input record. For example, the program: - awk '{ print $1 }' BBS-list + awk '{ print $1 }' mail-list prints the first field of every record. @@ -9673,13 +9686,13 @@ with a pound sign (`#'). $ awk 'BEGIN { > for (i = 0; i < ARGC; i++) > print ARGV[i] - > }' inventory-shipped BBS-list + > }' inventory-shipped mail-list -| awk -| inventory-shipped - -| BBS-list + -| mail-list `ARGV[0]' contains `awk', `ARGV[1]' contains `inventory-shipped', - and `ARGV[2]' contains `BBS-list'. The value of `ARGC' is three, + and `ARGV[2]' contains `mail-list'. The value of `ARGC' is three, one more than the index of the last element in `ARGV', because the elements are numbered from zero. @@ -10006,13 +10019,13 @@ information contained in `ARGC' and `ARGV': $ awk 'BEGIN { > for (i = 0; i < ARGC; i++) > print ARGV[i] - > }' inventory-shipped BBS-list + > }' inventory-shipped mail-list -| awk -| inventory-shipped - -| BBS-list + -| mail-list In this example, `ARGV[0]' contains `awk', `ARGV[1]' contains -`inventory-shipped', and `ARGV[2]' contains `BBS-list'. Notice that +`inventory-shipped', and `ARGV[2]' contains `mail-list'. Notice that the `awk' program is not entered in `ARGV'. The other command-line options, with their arguments, are also not entered. This includes variable assignments done with the `-v' option (*note Options::). @@ -25958,6 +25971,10 @@ Info file, in approximate chronological order: 4.1 was driven primarily by Arnold Robbins and Andrew Schorr, with notable contributions from the rest of the development team. + * Antonio Giovanni Colombo rewrote a number of examples in the early + chapters that were severely dated, for which I am incredibly + grateful. + * Arnold Robbins has been working on `gawk' since 1988, at first helping David Trueman, and as the primary maintainer since around 1994. @@ -28213,9 +28230,6 @@ Bash The GNU version of the standard shell (the Bourne-Again SHell). See also "Bourne Shell." -BBS - See "Bulletin Board System." - Bit Short for "Binary Digit." All values in computer memory ultimately reduce to binary digits: values that are either zero or @@ -28261,11 +28275,6 @@ Built-in Variable Braces See "Curly Braces." -Bulletin Board System - A computer system allowing users to log in and read and/or leave - messages for other users of the system, much like leaving paper - notes on a bulletin board. - C The system programming language that most GNU software is written in. The `awk' programming language has C-like syntax, and this @@ -30352,7 +30361,7 @@ Index (line 6) * artificial intelligence, gawk and: Distribution contents. (line 52) -* ASCII <1>: Glossary. (line 141) +* ASCII <1>: Glossary. (line 133) * ASCII: Ordinal Functions. (line 45) * asort() function (gawk) <1>: Array Sorting Functions. (line 6) @@ -30497,7 +30506,6 @@ Index (line 112) * backslash (\), in regexp constants: Computed Regexps. (line 28) * backtrace debugger command: Execution Stack. (line 13) -* BBS-list file: Sample Data Files. (line 6) * Beebe, Nelson H.F. <1>: Other Versions. (line 78) * Beebe, Nelson H.F.: Acknowledgments. (line 60) * BEGIN pattern <1>: Profiling. (line 62) @@ -30506,7 +30514,7 @@ Index * BEGIN pattern: Records. (line 29) * BEGIN pattern, assert() user-defined function and: Assert Function. (line 83) -* BEGIN pattern, Boolean patterns and: Expression Patterns. (line 73) +* BEGIN pattern, Boolean patterns and: Expression Patterns. (line 70) * BEGIN pattern, exit statement and: Exit Statement. (line 12) * BEGIN pattern, getline and: Getline Notes. (line 19) * BEGIN pattern, headings, adding: Print Examples. (line 43) @@ -30523,9 +30531,9 @@ Index * BEGIN pattern, TEXTDOMAIN variable and: Programmer i18n. (line 60) * BEGINFILE pattern: BEGINFILE/ENDFILE. (line 6) * BEGINFILE pattern, Boolean patterns and: Expression Patterns. - (line 73) + (line 70) * beginfile() user-defined function: Filetrans Function. (line 62) -* Bentley, Jon: Glossary. (line 151) +* Bentley, Jon: Glossary. (line 143) * Benzinger, Michael: Contributors. (line 97) * Berry, Karl <1>: Ranges and Locales. (line 74) * Berry, Karl: Acknowledgments. (line 33) @@ -30544,7 +30552,7 @@ Index * body, in actions: Statements. (line 10) * body, in loops: While Statement. (line 14) * Boolean expressions: Boolean Ops. (line 6) -* Boolean expressions, as patterns: Expression Patterns. (line 41) +* Boolean expressions, as patterns: Expression Patterns. (line 39) * Boolean operators, See Boolean expressions: Boolean Ops. (line 6) * Bourne shell, quoting rules for: Quoting. (line 18) * braces ({}): Profiling. (line 142) @@ -30593,7 +30601,7 @@ Index * Brini, Davide: Signature Program. (line 6) * Broder, Alan J.: Contributors. (line 88) * Brown, Martin: Contributors. (line 82) -* BSD-based operating systems: Glossary. (line 624) +* BSD-based operating systems: Glossary. (line 616) * bt debugger command (alias for backtrace): Execution Stack. (line 13) * Buening, Andreas <1>: Bugs. (line 71) * Buening, Andreas <2>: Contributors. (line 92) @@ -30636,7 +30644,7 @@ Index * character classes, See bracket expressions: Regexp Operators. (line 55) * character lists, See bracket expressions: Regexp Operators. (line 55) -* character sets (machine character encodings) <1>: Glossary. (line 141) +* character sets (machine character encodings) <1>: Glossary. (line 133) * character sets (machine character encodings): Ordinal Functions. (line 45) * character sets, See Also bracket expressions: Regexp Operators. @@ -30647,7 +30655,7 @@ Index * Chassell, Robert J.: Acknowledgments. (line 33) * chdir() extension function: Extension Sample File Functions. (line 12) -* chem utility: Glossary. (line 151) +* chem utility: Glossary. (line 143) * chr() extension function: Extension Sample Ord. (line 15) * chr() user-defined function: Ordinal Functions. (line 16) @@ -30670,6 +30678,7 @@ Index * Collado, Manuel: Acknowledgments. (line 60) * collating elements: Bracket Expressions. (line 69) * collating symbols: Bracket Expressions. (line 76) +* Colombo, Antonio <1>: Contributors. (line 135) * Colombo, Antonio: Acknowledgments. (line 60) * columns, aligning: Print Examples. (line 70) * columns, cutting: Cut Program. (line 6) @@ -30706,7 +30715,7 @@ Index * common extensions, func keyword: Definition Syntax. (line 83) * common extensions, length() applied to an array: String Functions. (line 193) -* common extensions, RS as a regexp: Records. (line 120) +* common extensions, RS as a regexp: Records. (line 135) * common extensions, single character fields: Single Character Fields. (line 6) * comp.lang.awk newsgroup: Bugs. (line 38) @@ -30722,7 +30731,7 @@ Index * compatibility mode (gawk), octal numbers: Nondecimal-numbers. (line 60) * compatibility mode (gawk), specifying: Options. (line 81) -* compiled programs <1>: Glossary. (line 165) +* compiled programs <1>: Glossary. (line 157) * compiled programs: Basic High Level. (line 15) * compiling gawk for Cygwin: Cygwin. (line 6) * compiling gawk for MS-DOS and MS-Windows: PC Compiling. (line 13) @@ -30764,7 +30773,7 @@ Index * CONVFMT variable: Conversion. (line 29) * CONVFMT variable, array subscripts and: Numeric Array Subscripts. (line 6) -* cookie: Glossary. (line 157) +* cookie: Glossary. (line 149) * coprocesses <1>: Two-way I/O. (line 44) * coprocesses: Redirection. (line 102) * coprocesses, closing: Close Files And Pipes. @@ -30783,7 +30792,7 @@ Index * cut.awk program: Cut Program. (line 45) * d debugger command (alias for delete): Breakpoint Control. (line 64) * d.c., See dark corner: Conventions. (line 38) -* dark corner <1>: Glossary. (line 197) +* dark corner <1>: Glossary. (line 189) * dark corner: Conventions. (line 38) * dark corner, "0" is actually true: Truth Values. (line 24) * dark corner, /= operator vs. /=.../ regexp constant: Assignment Ops. @@ -30810,7 +30819,7 @@ Index * dark corner, format-control characters: Control Letters. (line 18) * dark corner, FS as null string: Single Character Fields. (line 20) -* dark corner, input files: Records. (line 103) +* dark corner, input files: Records. (line 118) * dark corner, invoking awk: Command Line. (line 16) * dark corner, length() function: String Functions. (line 179) * dark corner, locale's decimal point character: Conversion. (line 77) @@ -30824,7 +30833,7 @@ Index * dark corner, regexp constants, as arguments to user-defined functions: Using Constant Regexps. (line 43) * dark corner, split() function: String Functions. (line 358) -* dark corner, strings, storing: Records. (line 195) +* dark corner, strings, storing: Records. (line 210) * dark corner, value of ARGV[0]: Auto-set. (line 35) * data, fixed-width: Constant Size. (line 10) * data-driven languages: Basic High Level. (line 85) @@ -31006,19 +31015,19 @@ Index * differences in awk and gawk, print/printf statements: Format Modifiers. (line 13) * differences in awk and gawk, PROCINFO array: Auto-set. (line 133) -* differences in awk and gawk, record separators: Records. (line 117) +* differences in awk and gawk, record separators: Records. (line 132) * differences in awk and gawk, regexp constants: Using Constant Regexps. (line 43) * differences in awk and gawk, regular expressions: Case-sensitivity. (line 26) -* differences in awk and gawk, RS/RT variables: Records. (line 172) +* differences in awk and gawk, RS/RT variables: Records. (line 187) * differences in awk and gawk, RT variable: Auto-set. (line 266) * differences in awk and gawk, single-character fields: Single Character Fields. (line 6) * differences in awk and gawk, split() function: String Functions. (line 346) * differences in awk and gawk, strings: Scalar Constants. (line 20) -* differences in awk and gawk, strings, storing: Records. (line 191) +* differences in awk and gawk, strings, storing: Records. (line 206) * differences in awk and gawk, SYMTAB variable: Auto-set. (line 274) * differences in awk and gawk, TEXTDOMAIN variable: User-modified. (line 162) @@ -31076,7 +31085,7 @@ Index * END pattern, assert() user-defined function and: Assert Function. (line 75) * END pattern, backslash continuation and: Egrep Program. (line 220) -* END pattern, Boolean patterns and: Expression Patterns. (line 73) +* END pattern, Boolean patterns and: Expression Patterns. (line 70) * END pattern, exit statement and: Exit Statement. (line 12) * END pattern, next/nextfile statements and <1>: Next Statement. (line 45) @@ -31085,7 +31094,7 @@ Index * END pattern, operators and: Using BEGIN/END. (line 17) * END pattern, print statement and: I/O And BEGIN/END. (line 16) * ENDFILE pattern: BEGINFILE/ENDFILE. (line 6) -* ENDFILE pattern, Boolean patterns and: Expression Patterns. (line 73) +* ENDFILE pattern, Boolean patterns and: Expression Patterns. (line 70) * endfile() user-defined function: Filetrans Function. (line 62) * endgrent() function (C library): Group Functions. (line 215) * endgrent() user-defined function: Group Functions. (line 218) @@ -31093,7 +31102,7 @@ Index * endpwent() user-defined function: Passwd Functions. (line 213) * ENVIRON array: Auto-set. (line 60) * environment variables: Auto-set. (line 60) -* epoch, definition of: Glossary. (line 243) +* epoch, definition of: Glossary. (line 235) * equals sign (=), = operator: Assignment Ops. (line 6) * equals sign (=), == operator <1>: Precedence. (line 65) * equals sign (=), == operator: Comparison Operators. @@ -31163,7 +31172,7 @@ Index * extensions, common, func keyword: Definition Syntax. (line 83) * extensions, common, length() applied to an array: String Functions. (line 193) -* extensions, common, RS as a regexp: Records. (line 120) +* extensions, common, RS as a regexp: Records. (line 135) * extensions, common, single character fields: Single Character Fields. (line 6) * extensions, in gawk, not in POSIX awk: POSIX/GNU. (line 6) @@ -31236,7 +31245,7 @@ Index * files, /inet/... (gawk): TCP/IP Networking. (line 6) * files, /inet4/... (gawk): TCP/IP Networking. (line 6) * files, /inet6/... (gawk): TCP/IP Networking. (line 6) -* files, as single records: Records. (line 204) +* files, as single records: Records. (line 219) * files, awk programs in: Long. (line 6) * files, awkprof.out: Profiling. (line 6) * files, awkvars.out: Options. (line 93) @@ -31316,10 +31325,10 @@ Index * frame debugger command: Execution Stack. (line 25) * Free Documentation License (FDL): GNU Free Documentation License. (line 6) -* Free Software Foundation (FSF) <1>: Glossary. (line 305) +* Free Software Foundation (FSF) <1>: Glossary. (line 297) * Free Software Foundation (FSF) <2>: Getting. (line 10) * Free Software Foundation (FSF): Manual History. (line 6) -* FreeBSD: Glossary. (line 624) +* FreeBSD: Glossary. (line 616) * FS variable <1>: User-modified. (line 56) * FS variable: Field Separators. (line 15) * FS variable, --field-separator option and: Options. (line 21) @@ -31332,7 +31341,7 @@ Index (line 6) * FS, containing ^: Regexp Field Splitting. (line 59) -* FSF (Free Software Foundation) <1>: Glossary. (line 305) +* FSF (Free Software Foundation) <1>: Glossary. (line 297) * FSF (Free Software Foundation) <2>: Getting. (line 10) * FSF (Free Software Foundation): Manual History. (line 6) * fts() extension function: Extension Sample File Functions. @@ -31466,7 +31475,7 @@ Index * gawk, RT variable in <2>: Getline/Variable/File. (line 10) * gawk, RT variable in <3>: Multiple Line. (line 129) -* gawk, RT variable in: Records. (line 117) +* gawk, RT variable in: Records. (line 132) * gawk, See Also awk: Preface. (line 36) * gawk, source code, obtaining: Getting. (line 6) * gawk, splitting fields and: Constant Size. (line 88) @@ -31480,7 +31489,7 @@ Index * gawk, word-boundary operator: GNU Regexp Operators. (line 63) * gawkextlib project: gawkextlib. (line 6) -* General Public License (GPL): Glossary. (line 314) +* General Public License (GPL): Glossary. (line 306) * General Public License, See GPL: Manual History. (line 11) * gensub() function (gawk) <1>: String Functions. (line 81) * gensub() function (gawk): Using Constant Regexps. @@ -31537,18 +31546,18 @@ Index * GNU awk, See gawk: Preface. (line 49) * GNU Free Documentation License: GNU Free Documentation License. (line 6) -* GNU General Public License: Glossary. (line 314) -* GNU Lesser General Public License: Glossary. (line 405) +* GNU General Public License: Glossary. (line 306) +* GNU Lesser General Public License: Glossary. (line 397) * GNU long options <1>: Options. (line 6) * GNU long options: Command Line. (line 13) * GNU long options, printing list of: Options. (line 154) -* GNU Project <1>: Glossary. (line 323) +* GNU Project <1>: Glossary. (line 315) * GNU Project: Manual History. (line 11) -* GNU/Linux <1>: Glossary. (line 624) +* GNU/Linux <1>: Glossary. (line 616) * GNU/Linux <2>: I18N Example. (line 55) * GNU/Linux: Manual History. (line 28) * Gordon, Assaf: Contributors. (line 105) -* GPL (General Public License) <1>: Glossary. (line 314) +* GPL (General Public License) <1>: Glossary. (line 306) * GPL (General Public License): Manual History. (line 11) * GPL (General Public License), printing: Options. (line 88) * grcat program: Group Functions. (line 16) @@ -31674,19 +31683,19 @@ Index * internationalization, localization, portability and: I18N Portability. (line 6) * internationalizing a program: Explaining gettext. (line 6) -* interpreted programs <1>: Glossary. (line 365) +* interpreted programs <1>: Glossary. (line 357) * interpreted programs: Basic High Level. (line 15) * interval expressions: Regexp Operators. (line 116) * inventory-shipped file: Sample Data Files. (line 32) * isarray() function (gawk): Type Functions. (line 11) -* ISO: Glossary. (line 376) -* ISO 8859-1: Glossary. (line 141) -* ISO Latin-1: Glossary. (line 141) +* ISO: Glossary. (line 368) +* ISO 8859-1: Glossary. (line 133) +* ISO Latin-1: Glossary. (line 133) * Jacobs, Andrew: Passwd Functions. (line 90) * Jaegermann, Michal <1>: Contributors. (line 45) * Jaegermann, Michal: Acknowledgments. (line 60) * Java implementation of awk: Other Versions. (line 112) -* Java programming language: Glossary. (line 388) +* Java programming language: Glossary. (line 380) * jawk: Other Versions. (line 112) * Jedi knights: Undocumented. (line 6) * join() user-defined function: Join Function. (line 18) @@ -31694,7 +31703,7 @@ Index * Kahrs, Ju"rgen: Acknowledgments. (line 60) * Kasal, Stepan: Acknowledgments. (line 60) * Kenobi, Obi-Wan: Undocumented. (line 6) -* Kernighan, Brian <1>: Glossary. (line 151) +* Kernighan, Brian <1>: Glossary. (line 143) * Kernighan, Brian <2>: Basic Data Typing. (line 55) * Kernighan, Brian <3>: Other Versions. (line 13) * Kernighan, Brian <4>: Contributors. (line 11) @@ -31735,8 +31744,8 @@ Index * left shift, bitwise: Bitwise Functions. (line 32) * leftmost longest match: Multiple Line. (line 26) * length() function: String Functions. (line 163) -* Lesser General Public License (LGPL): Glossary. (line 405) -* LGPL (Lesser General Public License): Glossary. (line 405) +* Lesser General Public License (LGPL): Glossary. (line 397) +* LGPL (Lesser General Public License): Glossary. (line 397) * libmawk: Other Versions. (line 120) * libraries of awk functions: Library Functions. (line 6) * libraries of awk functions, assertions: Assert Function. (line 6) @@ -31781,7 +31790,7 @@ Index * lint checking, undefined functions: Pass By Value/Reference. (line 88) * LINT variable: User-modified. (line 98) -* Linux <1>: Glossary. (line 624) +* Linux <1>: Glossary. (line 616) * Linux <2>: I18N Example. (line 55) * Linux: Manual History. (line 28) * list debugger command: Miscellaneous Debugger Commands. @@ -31813,6 +31822,7 @@ Index * ls utility: More Complex. (line 15) * lshift() function (gawk): Bitwise Functions. (line 46) * lvalues/rvalues: Assignment Ops. (line 32) +* mail-list file: Sample Data Files. (line 6) * mailing labels, printing: Labels Program. (line 6) * mailing list, GNITS: Acknowledgments. (line 52) * Malmberg, John <1>: Bugs. (line 72) @@ -31862,7 +31872,7 @@ Index * namespace issues, functions: Definition Syntax. (line 20) * nawk utility: Names. (line 17) * negative zero: Unexpected Results. (line 34) -* NetBSD: Glossary. (line 624) +* NetBSD: Glossary. (line 616) * networks, programming: TCP/IP Networking. (line 6) * networks, support for: Special Network. (line 6) * newlines <1>: Boolean Ops. (line 67) @@ -31909,7 +31919,7 @@ Index * null strings <2>: Truth Values. (line 6) * null strings <3>: Regexp Field Splitting. (line 43) -* null strings: Records. (line 107) +* null strings: Records. (line 122) * null strings, array elements and: Delete. (line 27) * null strings, as array subscripts: Uninitialized Subscripts. (line 43) @@ -31947,7 +31957,7 @@ Index * OFS variable <1>: User-modified. (line 124) * OFS variable <2>: Output Separators. (line 6) * OFS variable: Changing Fields. (line 64) -* OpenBSD: Glossary. (line 624) +* OpenBSD: Glossary. (line 616) * OpenSolaris: Other Versions. (line 96) * operating systems, BSD-based: Manual History. (line 28) * operating systems, PC, gawk on: PC Using. (line 6) @@ -32018,7 +32028,7 @@ Index * output, standard: Special FD. (line 6) * p debugger command (alias for print): Viewing And Changing Data. (line 36) -* P1003.1 POSIX standard: Glossary. (line 462) +* P1003.1 POSIX standard: Glossary. (line 454) * parentheses () <1>: Profiling. (line 146) * parentheses (): Regexp Operators. (line 79) * password file: Passwd Functions. (line 16) @@ -32031,7 +32041,7 @@ Index * patterns, empty: Empty. (line 6) * patterns, expressions as: Regexp Patterns. (line 6) * patterns, ranges in: Ranges. (line 6) -* patterns, regexp constants as: Expression Patterns. (line 36) +* patterns, regexp constants as: Expression Patterns. (line 34) * patterns, types of: Pattern Overview. (line 15) * pawk (profiling version of Brian Kernighan's awk): Other Versions. (line 78) @@ -32069,7 +32079,7 @@ Index (line 112) * portability, close() function and: Close Files And Pipes. (line 81) -* portability, data files as single record: Records. (line 179) +* portability, data files as single record: Records. (line 194) * portability, deleting array elements: Delete. (line 56) * portability, example programs: Library Functions. (line 42) * portability, functions, defining: Definition Syntax. (line 99) @@ -32209,7 +32219,7 @@ Index * programming languages, Ada: Glossary. (line 20) * programming languages, data-driven vs. procedural: Getting Started. (line 12) -* programming languages, Java: Glossary. (line 388) +* programming languages, Java: Glossary. (line 380) * programming, basic steps: Basic High Level. (line 20) * programming, concepts: Basic Concepts. (line 6) * pwcat program: Passwd Functions. (line 23) @@ -32260,16 +32270,16 @@ Index * recipe for a programming language: History. (line 6) * record separators <1>: User-modified. (line 143) * record separators: Records. (line 14) -* record separators, changing: Records. (line 81) -* record separators, regular expressions as: Records. (line 117) +* record separators, changing: Records. (line 93) +* record separators, regular expressions as: Records. (line 132) * record separators, with multiline records: Multiple Line. (line 10) * records <1>: Basic High Level. (line 73) * records: Reading Files. (line 14) * records, multiline: Multiple Line. (line 6) * records, printing: Print. (line 22) * records, splitting input into: Records. (line 6) -* records, terminating: Records. (line 117) -* records, treating files as: Records. (line 204) +* records, terminating: Records. (line 132) +* records, treating files as: Records. (line 219) * recursive functions: Definition Syntax. (line 73) * redirection of input: Getline/File. (line 6) * redirection of output: Redirection. (line 6) @@ -32280,7 +32290,7 @@ Index * regexp constants <2>: Regexp Constants. (line 6) * regexp constants: Regexp Usage. (line 57) * regexp constants, /=.../, /= operator and: Assignment Ops. (line 147) -* regexp constants, as patterns: Expression Patterns. (line 36) +* regexp constants, as patterns: Expression Patterns. (line 34) * regexp constants, in gawk: Using Constant Regexps. (line 28) * regexp constants, slashes vs. quotes: Computed Regexps. (line 28) @@ -32293,7 +32303,7 @@ Index (line 6) * regular expressions, as patterns <1>: Regexp Patterns. (line 6) * regular expressions, as patterns: Regexp Usage. (line 6) -* regular expressions, as record separators: Records. (line 117) +* regular expressions, as record separators: Records. (line 132) * regular expressions, case sensitivity <1>: User-modified. (line 82) * regular expressions, case sensitivity: Case-sensitivity. (line 6) * regular expressions, computed: Computed Regexps. (line 6) @@ -32346,13 +32356,13 @@ Index * RLENGTH variable, match() function and: String Functions. (line 220) * Robbins, Arnold <1>: Future Extensions. (line 6) * Robbins, Arnold <2>: Bugs. (line 32) -* Robbins, Arnold <3>: Contributors. (line 135) +* Robbins, Arnold <3>: Contributors. (line 139) * Robbins, Arnold <4>: General Data Types. (line 6) * Robbins, Arnold <5>: Alarm Program. (line 6) * Robbins, Arnold <6>: Passwd Functions. (line 90) * Robbins, Arnold <7>: Getline/Pipe. (line 39) * Robbins, Arnold: Command Line Field Separator. - (line 80) + (line 73) * Robbins, Bill: Getline/Pipe. (line 39) * Robbins, Harry: Acknowledgments. (line 78) * Robbins, Jean: Acknowledgments. (line 78) @@ -32376,7 +32386,7 @@ Index * RT variable <2>: Getline/Variable/File. (line 10) * RT variable <3>: Multiple Line. (line 129) -* RT variable: Records. (line 117) +* RT variable: Records. (line 132) * Rubin, Paul <1>: Contributors. (line 15) * Rubin, Paul: History. (line 30) * rule, definition of: Getting Started. (line 21) @@ -32421,7 +32431,7 @@ Index * separators, field, POSIX and: Fields. (line 6) * separators, for records <1>: User-modified. (line 143) * separators, for records: Records. (line 14) -* separators, for records, regular expressions as: Records. (line 117) +* separators, for records, regular expressions as: Records. (line 132) * separators, for statements in actions: Action Overview. (line 19) * separators, subscript: User-modified. (line 156) * set debugger command: Viewing And Changing Data. @@ -32471,7 +32481,7 @@ Index * sidebar, Piping into sh: Redirection. (line 140) * sidebar, Portability Issues with #!: Executable Scripts. (line 31) * sidebar, Recipe For A Programming Language: History. (line 6) -* sidebar, RS = "\0" Is Not Portable: Records. (line 177) +* sidebar, RS = "\0" Is Not Portable: Records. (line 192) * sidebar, So Why Does gawk have BEGINFILE and ENDFILE?: Filetrans Function. (line 83) * sidebar, Syntactic Ambiguities Between /= and Regular Expressions: Assignment Ops. @@ -32541,7 +32551,7 @@ Index * sqrt() function: Numeric Functions. (line 78) * square brackets ([]): Regexp Operators. (line 55) * srand() function: Numeric Functions. (line 82) -* Stallman, Richard <1>: Glossary. (line 305) +* Stallman, Richard <1>: Glossary. (line 297) * Stallman, Richard <2>: Contributors. (line 23) * Stallman, Richard <3>: Acknowledgments. (line 18) * Stallman, Richard: Manual History. (line 6) @@ -32571,7 +32581,7 @@ Index * strings, converting <1>: Bitwise Functions. (line 109) * strings, converting: Conversion. (line 6) * strings, converting, numbers to: User-modified. (line 28) -* strings, empty, See null strings: Records. (line 107) +* strings, empty, See null strings: Records. (line 122) * strings, extracting: String Extraction. (line 6) * strings, for localization: Programmer i18n. (line 14) * strings, length of: Scalar Constants. (line 20) @@ -32613,7 +32623,7 @@ Index * TCP/IP, support for: Special Network. (line 6) * tee utility: Tee Program. (line 6) * tee.awk program: Tee Program. (line 26) -* terminating records: Records. (line 117) +* terminating records: Records. (line 132) * testbits.awk program: Bitwise Functions. (line 70) * testext extension: Extension Sample API Tests. (line 6) @@ -32709,20 +32719,20 @@ Index * undisplay debugger command: Viewing And Changing Data. (line 80) * undocumented features: Undocumented. (line 6) -* Unicode <1>: Glossary. (line 141) +* Unicode <1>: Glossary. (line 133) * Unicode <2>: Ranges and Locales. (line 61) * Unicode: Ordinal Functions. (line 45) * uninitialized variables, as array subscripts: Uninitialized Subscripts. (line 6) * uniq utility: Uniq Program. (line 6) * uniq.awk program: Uniq Program. (line 65) -* Unix: Glossary. (line 624) +* Unix: Glossary. (line 616) * Unix awk, backslashes in escape sequences: Escape Sequences. (line 124) * Unix awk, close() function and: Close Files And Pipes. (line 130) * Unix awk, password files, field separators and: Command Line Field Separator. - (line 72) + (line 64) * Unix, awk scripts and: Executable Scripts. (line 6) * UNIXROOT variable, on OS/2 systems: PC Using. (line 16) * unsigned integers: General Arithmetic. (line 15) @@ -32887,499 +32897,499 @@ Node: Comments80254 Node: Quoting82721 Node: DOS Quoting87344 Node: Sample Data Files88019 -Node: Very Simple90405 -Node: Two Rules95004 -Node: More Complex97151 -Ref: More Complex-Footnote-1100081 -Node: Statements/Lines100166 -Ref: Statements/Lines-Footnote-1104628 -Node: Other Features104893 -Node: When105821 -Node: Invoking Gawk107968 -Node: Command Line109431 -Node: Options110214 -Ref: Options-Footnote-1125609 -Node: Other Arguments125634 -Node: Naming Standard Input128292 -Node: Environment Variables129386 -Node: AWKPATH Variable129944 -Ref: AWKPATH Variable-Footnote-1132702 -Node: AWKLIBPATH Variable132962 -Node: Other Environment Variables133680 -Node: Exit Status136643 -Node: Include Files137318 -Node: Loading Shared Libraries140887 -Node: Obsolete142251 -Node: Undocumented142948 -Node: Regexp143190 -Node: Regexp Usage144579 -Node: Escape Sequences146605 -Node: Regexp Operators152274 -Ref: Regexp Operators-Footnote-1159654 -Ref: Regexp 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No-one has such slow modems! @cindex input files, examples -@cindex @code{BBS-list} file +@cindex @code{mail-list} file Many of the examples in this @value{DOCUMENT} take their input from two sample -data files. The first, @file{BBS-list}, represents a list of -computer bulletin board systems together with information about those systems. +data files. The first, @file{mail-list}, represents a list of peoples' names +together with their email addresses and information about those people. The second data file, called @file{inventory-shipped}, contains information about monthly shipments. In both files, each line is considered to be one @dfn{record}. -In the data file @file{BBS-list}, each record contains the name of a computer -bulletin board, its phone number, the board's baud rate(s), and a code for -the number of hours it is operational. An @samp{A} in the last column -means the board operates 24 hours a day. A @samp{B} in the last -column means the board only operates on evening and weekend hours. -A @samp{C} means the board operates only on weekends: +In the data file @file{mail-list}, each record contains the name of a person, +his/her phone number, his/her email-address, and a code for their relationship +with the author of the list. An @samp{A} in the last column +means that the person is an acquaintance. An @samp{F} in the last +column means that the person is a friend. +An @samp{R} means that the person is a relative: -@c 2e: Update the baud rates to reflect today's faster modems @example @c system if test ! -d eg ; then mkdir eg ; fi @c system if test ! -d eg/lib ; then mkdir eg/lib ; fi @c system if test ! -d eg/data ; then mkdir eg/data ; fi @c system if test ! -d eg/prog ; then mkdir eg/prog ; fi @c system if test ! -d eg/misc ; then mkdir eg/misc ; fi -@c file eg/data/BBS-list -aardvark 555-5553 1200/300 B -alpo-net 555-3412 2400/1200/300 A -barfly 555-7685 1200/300 A -bites 555-1675 2400/1200/300 A -camelot 555-0542 300 C -core 555-2912 1200/300 C -fooey 555-1234 2400/1200/300 B -foot 555-6699 1200/300 B -macfoo 555-6480 1200/300 A -sdace 555-3430 2400/1200/300 A -sabafoo 555-2127 1200/300 C +@c file eg/data/mail-list +Amelia 555-5553 amelia.zodiacusque@@gmail.com F +Anthony 555-3412 anthony.asserturo@@hotmail.com A +Becky 555-7685 becky.algebrarum@@gmail.com A +Bill 555-1675 bill.drowning@@hotmail.com A +Broderick 555-0542 broderick.aliquotiens@@yahoo.com R +Camilla 555-2912 camilla.infusarum@@skynet.be R +Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +Julie 555-6699 julie.perscrutabor@@skeeve.com F +Martin 555-6480 martin.codicibus@@hotmail.com A +Samuel 555-3430 samuel.lanceolis@@shu.edu A +Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @c endfile @end example @@ -2630,23 +2629,23 @@ in the directory @file{awklib/eg/data}. @section Some Simple Examples The following command runs a simple @command{awk} program that searches the -input file @file{BBS-list} for the character string @samp{foo} (a +input file @file{mail-list} for the character string @samp{li} (a grouping of characters is usually called a @dfn{string}; the term @dfn{string} is based on similar usage in English, such as ``a string of pearls,'' or ``a string of cars in a train''): @example -awk '/foo/ @{ print $0 @}' BBS-list +awk '/li/ @{ print $0 @}' mail-list @end example @noindent -When lines containing @samp{foo} are found, they are printed because +When lines containing @samp{li} are found, they are printed because @w{@samp{print $0}} means print the current line. (Just @samp{print} by itself means the same thing, so we could have written that instead.) -You will notice that slashes (@samp{/}) surround the string @samp{foo} -in the @command{awk} program. The slashes indicate that @samp{foo} +You will notice that slashes (@samp{/}) surround the string @samp{li} +in the @command{awk} program. The slashes indicate that @samp{li} is the pattern to search for. This type of pattern is called a @dfn{regular expression}, which is covered in more detail later (@pxref{Regexp}). @@ -2658,11 +2657,11 @@ interpret any of it as special shell characters. Here is what this program prints: @example -$ @kbd{awk '/foo/ @{ print $0 @}' BBS-list} -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sabafoo 555-2127 1200/300 C +$ @kbd{awk '/li/ @{ print $0 @}' mail-list} +@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F +@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R +@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F +@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A @end example @cindex actions, default @@ -2675,7 +2674,7 @@ action is to print all lines that match the pattern. @cindex actions, empty Thus, we could leave out the action (the @code{print} statement and the curly braces) in the previous example and the result would be the same: -@command{awk} prints all lines matching the pattern @samp{foo}. By comparison, +@command{awk} prints all lines matching the pattern @samp{li}. By comparison, omitting the @code{print} statement but retaining the curly braces makes an empty action that does nothing (i.e., no lines are printed). @@ -2820,29 +2819,23 @@ This program prints every line that contains the string strings, it is printed twice, once by each rule. This is what happens if we run this program on our two sample data files, -@file{BBS-list} and @file{inventory-shipped}: +@file{mail-list} and @file{inventory-shipped}: @example $ @kbd{awk '/12/ @{ print $0 @}} -> @kbd{/21/ @{ print $0 @}' BBS-list inventory-shipped} -@print{} aardvark 555-5553 1200/300 B -@print{} alpo-net 555-3412 2400/1200/300 A -@print{} barfly 555-7685 1200/300 A -@print{} bites 555-1675 2400/1200/300 A -@print{} core 555-2912 1200/300 C -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sdace 555-3430 2400/1200/300 A -@print{} sabafoo 555-2127 1200/300 C -@print{} sabafoo 555-2127 1200/300 C +> @kbd{/21/ @{ print $0 @}' mail-list inventory-shipped} +@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A +@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R +@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @print{} Jan 21 36 64 620 @print{} Apr 21 70 74 514 @end example @noindent -Note how the line beginning with @samp{sabafoo} -in @file{BBS-list} was printed twice, once for each rule. +Note how the line beginning with @samp{Jean-Paul} +in @file{mail-list} was printed twice, once for each rule. @node More Complex @section A More Complex Example @@ -2921,7 +2914,7 @@ separate rule, like this: @example awk '/12/ @{ print $0 @} - /21/ @{ print $0 @}' BBS-list inventory-shipped + /21/ @{ print $0 @}' mail-list inventory-shipped @end example @cindex @command{gawk}, newlines in @@ -4331,14 +4324,14 @@ slashes. Then the regular expression is tested against the entire text of each record. (Normally, it only needs to match some part of the text in order to succeed.) For example, the following prints the second field of each record that contains the string -@samp{foo} anywhere in it: +@samp{li} anywhere in it: @example -$ @kbd{awk '/foo/ @{ print $2 @}' BBS-list} -@print{} 555-1234 +$ @kbd{awk '/li/ @{ print $2 @}' mail-list} +@print{} 555-5553 +@print{} 555-0542 @print{} 555-6699 -@print{} 555-6480 -@print{} 555-2127 +@print{} 555-3430 @end example @cindex regular expressions, operators @@ -5647,66 +5640,78 @@ For example: @cindex @code{BEGIN} pattern @example -awk 'BEGIN @{ RS = "/" @} - @{ print $0 @}' BBS-list +awk 'BEGIN @{ RS = "u" @} + @{ print $0 @}' mail-list @end example @noindent -changes the value of @code{RS} to @code{"/"}, before reading any input. -This is a string whose first character is a slash; as a result, records -are separated by slashes. Then the input file is read, and the second +changes the value of @code{RS} to @samp{u}, before reading any input. +This is a string whose first character is the letter ``u;'' as a result, records +are separated by the letter ``u.'' Then the input file is read, and the second rule in the @command{awk} program (the action with no pattern) prints each record. Because each @code{print} statement adds a newline at the end of its output, this @command{awk} program copies the input -with each slash changed to a newline. Here are the results of running -the program on @file{BBS-list}: - -@example -$ @kbd{awk 'BEGIN @{ RS = "/" @}} -> @kbd{@{ print $0 @}' BBS-list} -@print{} aardvark 555-5553 1200 -@print{} 300 B -@print{} alpo-net 555-3412 2400 -@print{} 1200 -@print{} 300 A -@print{} barfly 555-7685 1200 -@print{} 300 A -@print{} bites 555-1675 2400 -@print{} 1200 -@print{} 300 A -@print{} camelot 555-0542 300 C -@print{} core 555-2912 1200 -@print{} 300 C -@print{} fooey 555-1234 2400 -@print{} 1200 -@print{} 300 B -@print{} foot 555-6699 1200 -@print{} 300 B -@print{} macfoo 555-6480 1200 -@print{} 300 A -@print{} sdace 555-3430 2400 -@print{} 1200 -@print{} 300 A -@print{} sabafoo 555-2127 1200 -@print{} 300 C -@print{} +with each @samp{u} changed to a newline. Here are the results of running +the program on @file{mail-list}: + +@example +$ @kbd{awk 'BEGIN @{ RS = "u" @}} +> @kbd{@{ print $0 @}' mail-list} +@print{} Amelia 555-5553 amelia.zodiac +@print{} sq +@print{} e@@gmail.com F +@print{} Anthony 555-3412 anthony.assert +@print{} ro@@hotmail.com A +@print{} Becky 555-7685 becky.algebrar +@print{} m@@gmail.com A +@print{} Bill 555-1675 bill.drowning@@hotmail.com A +@print{} Broderick 555-0542 broderick.aliq +@print{} otiens@@yahoo.com R +@print{} Camilla 555-2912 camilla.inf +@print{} sar +@print{} m@@skynet.be R +@print{} Fabi +@print{} s 555-1234 fabi +@print{} s. +@print{} ndevicesim +@print{} s@@ +@print{} cb.ed +@print{} F +@print{} J +@print{} lie 555-6699 j +@print{} lie.perscr +@print{} tabor@@skeeve.com F +@print{} Martin 555-6480 martin.codicib +@print{} s@@hotmail.com A +@print{} Sam +@print{} el 555-3430 sam +@print{} el.lanceolis@@sh +@print{} .ed +@print{} A +@print{} Jean-Pa +@print{} l 555-2127 jeanpa +@print{} l.campanor +@print{} m@@ny +@print{} .ed +@print{} R +@print{} @end example @noindent -Note that the entry for the @samp{camelot} BBS is not split. +Note that the entry for the name @samp{Bill} is not split. In the original data file (@pxref{Sample Data Files}), the line looks like this: @example -camelot 555-0542 300 C +Bill 555-1675 bill.drowning@@hotmail.com A @end example @noindent -It has one baud rate only, so there are no slashes in the record, -unlike the others which have two or more baud rates. -In fact, this record is treated as part of the record -for the @samp{core} BBS; the newline separating them in the output +It contains no @samp{u} so there is no reason to split the record, +unlike the others which have one or more occurrences of the @samp{u}. +In fact, this record is treated as part of the previous record; +the newline separating them in the output is the original newline in the data file, not the one added by @command{awk} when it printed the record! @@ -5717,14 +5722,17 @@ using the variable-assignment feature (@pxref{Other Arguments}): @example -awk '@{ print $0 @}' RS="/" BBS-list +awk '@{ print $0 @}' RS="u" mail-list @end example @noindent -This sets @code{RS} to @samp{/} before processing @file{BBS-list}. +This sets @code{RS} to @samp{u} before processing @file{mail-list}. -Using an unusual character such as @samp{/} for the record separator -produces correct behavior in the vast majority of cases. +Using an alphabetic character such as @samp{u} for the record separator +is highly likely to produce strange results. +Using an unusual character such as @samp{/} is more likely to +produce correct behavior in the majority of cases, but there +are no guarantees. The moral is: Know Your Data. There is one unusual case, that occurs when @command{gawk} is being fully POSIX-compliant (@pxref{Options}). @@ -6011,31 +6019,29 @@ when you are not interested in specific fields. Here are some more examples: @example -$ @kbd{awk '$1 ~ /foo/ @{ print $0 @}' BBS-list} -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sabafoo 555-2127 1200/300 C +$ @kbd{awk '$1 ~ /li/ @{ print $0 @}' mail-list} +@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F +@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F @end example @noindent -This example prints each record in the file @file{BBS-list} whose first -field contains the string @samp{foo}. The operator @samp{~} is called a +This example prints each record in the file @file{mail-list} whose first +field contains the string @samp{li}. The operator @samp{~} is called a @dfn{matching operator} (@pxref{Regexp Usage}); it tests whether a string (here, the field @code{$1}) matches a given regular expression. By contrast, the following example -looks for @samp{foo} in @emph{the entire record} and prints the first +looks for @samp{li} in @emph{the entire record} and prints the first field and the last field for each matching input record: @example -$ @kbd{awk '/foo/ @{ print $1, $NF @}' BBS-list} -@print{} fooey B -@print{} foot B -@print{} macfoo A -@print{} sabafoo C +$ @kbd{awk '/li/ @{ print $1, $NF @}' mail-list} +@print{} Amelia F +@print{} Broderick R +@print{} Julie F +@print{} Samuel A @end example @c ENDOFRANGE fiex @@ -6063,7 +6069,7 @@ the record has fewer than 20 fields, so this prints a blank line. Here is another example of using expressions as field numbers: @example -awk '@{ print $(2*2) @}' BBS-list +awk '@{ print $(2*2) @}' mail-list @end example @command{awk} evaluates the expression @samp{(2*2)} and uses @@ -6072,8 +6078,8 @@ represents multiplication, so the expression @samp{2*2} evaluates to four. The parentheses are used so that the multiplication is done before the @samp{$} operation; they are necessary whenever there is a binary operator in the field-number expression. This example, then, prints the -hours of operation (the fourth field) for every line of the file -@file{BBS-list}. (All of the @command{awk} operators are listed, in +type of relationship (the fourth field) for every line of the file +@file{mail-list}. (All of the @command{awk} operators are listed, in order of decreasing precedence, in @ref{Precedence}.) @@ -6635,66 +6641,59 @@ figures that you really want your fields to be separated with TABs and not @samp{t}s. Use @samp{-v FS="t"} or @samp{-F"[t]"} on the command line if you really do want to separate your fields with @samp{t}s. -As an example, let's use an @command{awk} program file called @file{baud.awk} -that contains the pattern @code{/300/} and the action @samp{print $1}: +As an example, let's use an @command{awk} program file called @file{edu.awk} +that contains the pattern @code{/edu/} and the action @samp{print $1}: @example -/300/ @{ print $1 @} +/edu/ @{ print $1 @} @end example Let's also set @code{FS} to be the @samp{-} character and run the -program on the file @file{BBS-list}. The following command prints a -list of the names of the bulletin boards that operate at 300 baud and +program on the file @file{mail-list}. The following command prints a +list of the names of the people that work at or attend a university, and the first three digits of their phone numbers: @c tweaked to make the tex output look better in @smallbook @example -$ @kbd{awk -F- -f baud.awk BBS-list} -@print{} aardvark 555 -@print{} alpo -@print{} barfly 555 -@print{} bites 555 -@print{} camelot 555 -@print{} core 555 -@print{} fooey 555 -@print{} foot 555 -@print{} macfoo 555 -@print{} sdace 555 -@print{} sabafoo 555 +$ @kbd{awk -F- -f edu.awk mail-list} +@print{} Fabius 555 +@print{} Samuel 555 +@print{} Jean @end example @noindent -Note the second line of output. The second line +Note the third line of output. The third line in the original file looked like this: @example -alpo-net 555-3412 2400/1200/300 A +Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @end example -The @samp{-} as part of the system's name was used as the field +The @samp{-} as part of the person's name was used as the field separator, instead of the @samp{-} in the phone number that was originally intended. This demonstrates why you have to be careful in choosing your field and record separators. @cindex Unix @command{awk}, password files@comma{} field separators and -Perhaps the most common use of a single character as the field -separator occurs when processing the Unix system password file. -On many Unix systems, each user has a separate entry in the system password -file, one line per user. The information in these lines is separated -by colons. The first field is the user's login name and the second is -the user's (encrypted or shadow) password. A password file entry might look -like this: +Perhaps the most common use of a single character as the field separator +occurs when processing the Unix system password file. On many Unix +systems, each user has a separate entry in the system password file, one +line per user. The information in these lines is separated by colons. +The first field is the user's login name and the second is the user's +encrypted or shadow password. (A shadow password is indicated by the +presence of a single @samp{x} in the second field.) A password file +entry might look like this: @cindex Robbins, Arnold @example -arnold:xyzzy:2076:10:Arnold Robbins:/home/arnold:/bin/bash +arnold:x:2076:10:Arnold Robbins:/home/arnold:/bin/bash @end example The following program searches the system password file and prints -the entries for users who have no password: +the entries for users whose full name is not indicated: @example -awk -F: '$2 == ""' /etc/passwd +awk -F: '$5 == ""' /etc/passwd @end example @node Full Line Fields @@ -8265,13 +8264,29 @@ program by using a new value of @code{OFS}. @example $ @kbd{awk 'BEGIN @{ OFS = ";"; ORS = "\n\n" @}} -> @kbd{@{ print $1, $2 @}' BBS-list} -@print{} aardvark;555-5553 -@print{} -@print{} alpo-net;555-3412 -@print{} -@print{} barfly;555-7685 -@dots{} +> @kbd{@{ print $1, $2 @}' mail-list} +@print{} Amelia;555-5553 +@print{} +@print{} Anthony;555-3412 +@print{} +@print{} Becky;555-7685 +@print{} +@print{} Bill;555-1675 +@print{} +@print{} Broderick;555-0542 +@print{} +@print{} Camilla;555-2912 +@print{} +@print{} Fabius;555-1234 +@print{} +@print{} Julie;555-6699 +@print{} +@print{} Martin;555-6480 +@print{} +@print{} Samuel;555-3430 +@print{} +@print{} Jean-Paul;555-2127 +@print{} @end example If the value of @code{ORS} does not contain a newline, the program's output @@ -8745,30 +8760,30 @@ The following simple example shows how to use @code{printf} to make an aligned table: @example -awk '@{ printf "%-10s %s\n", $1, $2 @}' BBS-list +awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list @end example @noindent This command -prints the names of the bulletin boards (@code{$1}) in the file -@file{BBS-list} as a string of 10 characters that are left-justified. It also +prints the names of the people (@code{$1}) in the file +@file{mail-list} as a string of 10 characters that are left-justified. It also prints the phone numbers (@code{$2}) next on the line. This produces an aligned two-column table of names and phone numbers, as shown here: @example -$ @kbd{awk '@{ printf "%-10s %s\n", $1, $2 @}' BBS-list} -@print{} aardvark 555-5553 -@print{} alpo-net 555-3412 -@print{} barfly 555-7685 -@print{} bites 555-1675 -@print{} camelot 555-0542 -@print{} core 555-2912 -@print{} fooey 555-1234 -@print{} foot 555-6699 -@print{} macfoo 555-6480 -@print{} sdace 555-3430 -@print{} sabafoo 555-2127 +$ @kbd{awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list} +@print{} Amelia 555-5553 +@print{} Anthony 555-3412 +@print{} Becky 555-7685 +@print{} Bill 555-1675 +@print{} Broderick 555-0542 +@print{} Camilla 555-2912 +@print{} Fabius 555-1234 +@print{} Julie 555-6699 +@print{} Martin 555-6480 +@print{} Samuel 555-3430 +@print{} Jean-Paul 555-2127 @end example In this case, the phone numbers had to be printed as strings because @@ -8789,7 +8804,7 @@ the @command{awk} program: @example awk 'BEGIN @{ print "Name Number" print "---- ------" @} - @{ printf "%-10s %s\n", $1, $2 @}' BBS-list + @{ printf "%-10s %s\n", $1, $2 @}' mail-list @end example The above example mixes @code{print} and @code{printf} statements in @@ -8799,7 +8814,7 @@ same results: @example awk 'BEGIN @{ printf "%-10s %s\n", "Name", "Number" printf "%-10s %s\n", "----", "------" @} - @{ printf "%-10s %s\n", $1, $2 @}' BBS-list + @{ printf "%-10s %s\n", $1, $2 @}' mail-list @end example @noindent @@ -8814,7 +8829,7 @@ emphasized by storing it in a variable, like this: awk 'BEGIN @{ format = "%-10s %s\n" printf format, "Name", "Number" printf format, "----", "------" @} - @{ printf format, $1, $2 @}' BBS-list + @{ printf format, $1, $2 @}' mail-list @end example @c !!! exercise @@ -8871,20 +8886,20 @@ before the first output is written to it. Subsequent writes to the same @var{output-file} do not erase @var{output-file}, but append to it. (This is different from how you use redirections in shell scripts.) If @var{output-file} does not exist, it is created. For example, here -is how an @command{awk} program can write a list of BBS names to one +is how an @command{awk} program can write a list of peoples' names to one file named @file{name-list}, and a list of phone numbers to another file named @file{phone-list}: @example $ @kbd{awk '@{ print $2 > "phone-list"} -> @kbd{print $1 > "name-list" @}' BBS-list} +> @kbd{print $1 > "name-list" @}' mail-list} $ @kbd{cat phone-list} @print{} 555-5553 @print{} 555-3412 @dots{} $ @kbd{cat name-list} -@print{} aardvark -@print{} alpo-net +@print{} Amelia +@print{} Anthony @dots{} @end example @@ -8913,7 +8928,7 @@ to another process created to execute @var{command}. The redirection argument @var{command} is actually an @command{awk} expression. Its value is converted to a string whose contents give the shell command to be run. For example, the following produces two -files, one unsorted list of BBS names, and one list sorted in reverse +files, one unsorted list of peoples' names, and one list sorted in reverse alphabetical order: @ignore @@ -8926,7 +8941,7 @@ alone for now and let's hope no-one notices. @example awk '@{ print $1 > "names.unsorted" command = "sort -r > names.sorted" - print $1 | command @}' BBS-list + print $1 | command @}' mail-list @end example The unsorted list is written with an ordinary redirection, while @@ -9997,7 +10012,7 @@ its position among the input file arguments---after the processing of the preceding input file argument. For example: @example -awk '@{ print $n @}' n=4 inventory-shipped n=2 BBS-list +awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list @end example @noindent @@ -10006,10 +10021,10 @@ the first file is read, the command line sets the variable @code{n} equal to four. This causes the fourth field to be printed in lines from @file{inventory-shipped}. After the first file has finished, but before the second file is started, @code{n} is set to two, so that the -second field is printed in lines from @file{BBS-list}: +second field is printed in lines from @file{mail-list}: @example -$ @kbd{awk '@{ print $n @}' n=4 inventory-shipped n=2 BBS-list} +$ @kbd{awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list} @print{} 15 @print{} 24 @dots{} @@ -10332,9 +10347,9 @@ specific operator to represent it. Instead, concatenation is performed by writing expressions next to one another, with no operator. For example: @example -$ @kbd{awk '@{ print "Field number one: " $1 @}' BBS-list} -@print{} Field number one: aardvark -@print{} Field number one: alpo-net +$ @kbd{awk '@{ print "Field number one: " $1 @}' mail-list} +@print{} Field number one: Amelia +@print{} Field number one: Anthony @dots{} @end example @@ -10342,9 +10357,9 @@ Without the space in the string constant after the @samp{:}, the line runs together. For example: @example -$ @kbd{awk '@{ print "Field number one:" $1 @}' BBS-list} -@print{} Field number one:aardvark -@print{} Field number one:alpo-net +$ @kbd{awk '@{ print "Field number one:" $1 @}' mail-list} +@print{} Field number one:Amelia +@print{} Field number one:Anthony @dots{} @end example @@ -11419,10 +11434,10 @@ The Boolean operators are: @item @var{boolean1} && @var{boolean2} True if both @var{boolean1} and @var{boolean2} are true. For example, the following statement prints the current input record if it contains -both @samp{2400} and @samp{foo}: +both @samp{edu} and @samp{li}: @example -if ($0 ~ /2400/ && $0 ~ /foo/) print +if ($0 ~ /edu/ && $0 ~ /li/) print @end example @cindex side effects, Boolean operators @@ -11435,11 +11450,11 @@ no substring @samp{foo} in the record. @item @var{boolean1} || @var{boolean2} True if at least one of @var{boolean1} or @var{boolean2} is true. For example, the following statement prints all records in the input -that contain @emph{either} @samp{2400} or -@samp{foo} or both: +that contain @emph{either} @samp{edu} or +@samp{li} or both: @example -if ($0 ~ /2400/ || $0 ~ /foo/) print +if ($0 ~ /edu/ || $0 ~ /li/) print @end example The subexpression @var{boolean2} is evaluated only if @var{boolean1} @@ -12034,7 +12049,7 @@ slashes (@code{/@var{regexp}/}), or any expression whose string value is used as a dynamic regular expression (@pxref{Computed Regexps}). The following example prints the second field of each input record -whose first field is precisely @samp{foo}: +whose first field is precisely @samp{li}: @cindex @code{/} (forward slash), patterns and @cindex forward slash (@code{/}), patterns and @@ -12043,68 +12058,65 @@ whose first field is precisely @samp{foo}: @cindex @code{!} (exclamation point), @code{!~} operator @cindex exclamation point (@code{!}), @code{!~} operator @example -$ @kbd{awk '$1 == "foo" @{ print $2 @}' BBS-list} +$ @kbd{awk '$1 == "li" @{ print $2 @}' mail-list} @end example @noindent -(There is no output, because there is no BBS site with the exact name @samp{foo}.) +(There is no output, because there is no person with the exact name @samp{li}.) Contrast this with the following regular expression match, which -accepts any record with a first field that contains @samp{foo}: +accepts any record with a first field that contains @samp{li}: @example -$ @kbd{awk '$1 ~ /foo/ @{ print $2 @}' BBS-list} -@print{} 555-1234 +$ @kbd{awk '$1 ~ /foo/ @{ print $2 @}' mail-list} +@print{} 555-5553 @print{} 555-6699 -@print{} 555-6480 -@print{} 555-2127 @end example @cindex regexp constants, as patterns @cindex patterns, regexp constants as A regexp constant as a pattern is also a special case of an expression -pattern. The expression @code{/foo/} has the value one if @samp{foo} -appears in the current input record. Thus, as a pattern, @code{/foo/} -matches any record containing @samp{foo}. +pattern. The expression @code{/li/} has the value one if @samp{li} +appears in the current input record. Thus, as a pattern, @code{/li/} +matches any record containing @samp{li}. @cindex Boolean expressions, as patterns Boolean expressions are also commonly used as patterns. Whether the pattern matches an input record depends on whether its subexpressions match. For example, the following command prints all the records in -@file{BBS-list} that contain both @samp{2400} and @samp{foo}: +@file{mail-list} that contain both @samp{edu} and @samp{li}: @example -$ @kbd{awk '/2400/ && /foo/' BBS-list} -@print{} fooey 555-1234 2400/1200/300 B +$ @kbd{awk '/edu/ && /li/' mail-list} +@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A @end example The following command prints all records in -@file{BBS-list} that contain @emph{either} @samp{2400} or @samp{foo} +@file{mail-list} that contain @emph{either} @samp{edu} or @samp{li} (or both, of course): @example -$ @kbd{awk '/2400/ || /foo/' BBS-list} -@print{} alpo-net 555-3412 2400/1200/300 A -@print{} bites 555-1675 2400/1200/300 A -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sdace 555-3430 2400/1200/300 A -@print{} sabafoo 555-2127 1200/300 C +$ @kbd{awk '/edu/ || /li/' mail-list} +@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F +@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R +@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F +@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @end example The following command prints all records in -@file{BBS-list} that do @emph{not} contain the string @samp{foo}: +@file{mail-list} that do @emph{not} contain the string @samp{li}: @example -$ @kbd{awk '! /foo/' BBS-list} -@print{} aardvark 555-5553 1200/300 B -@print{} alpo-net 555-3412 2400/1200/300 A -@print{} barfly 555-7685 1200/300 A -@print{} bites 555-1675 2400/1200/300 A -@print{} camelot 555-0542 300 C -@print{} core 555-2912 1200/300 C -@print{} sdace 555-3430 2400/1200/300 A +$ @kbd{awk '! /li/' mail-list} +@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A +@print{} Becky 555-7685 becky.algebrarum@@gmail.com A +@print{} Bill 555-1675 bill.drowning@@hotmail.com A +@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R +@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +@print{} Martin 555-6480 martin.codicibus@@hotmail.com A +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @end example @cindex @code{BEGIN} pattern, Boolean patterns and @@ -12243,22 +12255,22 @@ input is read. For example: @example $ @kbd{awk '} -> @kbd{BEGIN @{ print "Analysis of \"foo\"" @}} -> @kbd{/foo/ @{ ++n @}} -> @kbd{END @{ print "\"foo\" appears", n, "times." @}' BBS-list} -@print{} Analysis of "foo" -@print{} "foo" appears 4 times. +> @kbd{BEGIN @{ print "Analysis of \"li\"" @}} +> @kbd{/li/ @{ ++n @}} +> @kbd{END @{ print "\"li\" appears in", n, "records." @}' mail-list} +@print{} Analysis of "li" +@print{} "li" appears in 4 records. @end example @cindex @code{BEGIN} pattern, operators and @cindex @code{END} pattern, operators and -This program finds the number of records in the input file @file{BBS-list} -that contain the string @samp{foo}. The @code{BEGIN} rule prints a title +This program finds the number of records in the input file @file{mail-list} +that contain the string @samp{li}. The @code{BEGIN} rule prints a title for the report. There is no need to use the @code{BEGIN} rule to initialize the counter @code{n} to zero, since @command{awk} does this automatically (@pxref{Variables}). The second rule increments the variable @code{n} every time a -record containing the pattern @samp{foo} is read. The @code{END} rule +record containing the pattern @samp{li} is read. The @code{END} rule prints the value of @code{n} at the end of the run. The special patterns @code{BEGIN} and @code{END} cannot be used in ranges @@ -12422,7 +12434,7 @@ both @code{BEGINFILE} and @code{ENDFILE}. Only the @samp{getline In most other @command{awk} implementations, or if @command{gawk} is in compatibility mode (@pxref{Options}), they are not special. -@c FIXME: For 4.1 maybe deal with this? +@c FIXME: For 4.2 maybe deal with this? @ignore Date: Tue, 17 May 2011 02:06:10 PDT From: rankin@pactechdata.com (Pat Rankin) @@ -12453,7 +12465,7 @@ An empty (i.e., nonexistent) pattern is considered to match @emph{every} input record. For example, the program: @example -awk '@{ print $1 @}' BBS-list +awk '@{ print $1 @}' mail-list @end example @noindent @@ -13655,16 +13667,16 @@ In the following example: $ @kbd{awk 'BEGIN @{} > @kbd{for (i = 0; i < ARGC; i++)} > @kbd{print ARGV[i]} -> @kbd{@}' inventory-shipped BBS-list} +> @kbd{@}' inventory-shipped mail-list} @print{} awk @print{} inventory-shipped -@print{} BBS-list +@print{} mail-list @end example @noindent @code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]} contains @samp{inventory-shipped}, and @code{ARGV[2]} contains -@samp{BBS-list}. The value of @code{ARGC} is three, one more than the +@samp{mail-list}. The value of @code{ARGC} is three, one more than the index of the last element in @code{ARGV}, because the elements are numbered from zero. @@ -14131,16 +14143,16 @@ and @code{ARGV}: $ @kbd{awk 'BEGIN @{} > @kbd{for (i = 0; i < ARGC; i++)} > @kbd{print ARGV[i]} -> @kbd{@}' inventory-shipped BBS-list} +> @kbd{@}' inventory-shipped mail-list} @print{} awk @print{} inventory-shipped -@print{} BBS-list +@print{} mail-list @end example @noindent In this example, @code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]} contains @samp{inventory-shipped}, and @code{ARGV[2]} contains -@samp{BBS-list}. +@samp{mail-list}. Notice that the @command{awk} program is not entered in @code{ARGV}. The other command-line options, with their arguments, are also not entered. This includes variable assignments done with the @option{-v} @@ -34744,6 +34756,11 @@ Arnold Robbins and Andrew Schorr, with notable contributions from the rest of the development team. @item +@cindex Colombo, Antonio +Antonio Giovanni Colombo rewrote a number of examples in the early +chapters that were severely dated, for which I am incredibly grateful. + +@item @cindex Robbins, Arnold Arnold Robbins has been working on @command{gawk} since 1988, at first @@ -37484,9 +37501,6 @@ The GNU version of the standard shell @end ifinfo See also ``Bourne Shell.'' -@item BBS -See ``Bulletin Board System.'' - @item Bit Short for ``Binary Digit.'' All values in computer memory ultimately reduce to binary digits: values @@ -37561,11 +37575,6 @@ Changing some of them affects @command{awk}'s running environment. @item Braces See ``Curly Braces.'' -@item Bulletin Board System -A computer system allowing users to log in and read and/or leave messages -for other users of the system, much like leaving paper notes on a bulletin -board. - @item C The system programming language that most GNU software is written in. The @command{awk} programming language has C-like syntax, and this @value{DOCUMENT} @@ -39531,8 +39540,6 @@ Suggestions: % Next edition: % 1. Standardize the error messages from the functions and programs % in the two sample code chapters. -% 2. Nuke the BBS stuff and use something that won't be obsolete -% 3. Turn the advanced notes into sidebars by using @cartouche Better sidebars can almost sort of be done with: @@ -39564,4 +39571,3 @@ But to use it you have to say } which sorta sucks. - diff --git a/doc/gawktexi.in b/doc/gawktexi.in index 1fe75843..9a5c0168 100644 --- a/doc/gawktexi.in +++ b/doc/gawktexi.in @@ -2483,40 +2483,39 @@ gawk "@{ print \"\042\" $0 \"\042\" @}" @var{file} @c For gawk >= 4.0, update these data files. No-one has such slow modems! @cindex input files, examples -@cindex @code{BBS-list} file +@cindex @code{mail-list} file Many of the examples in this @value{DOCUMENT} take their input from two sample -data files. The first, @file{BBS-list}, represents a list of -computer bulletin board systems together with information about those systems. +data files. The first, @file{mail-list}, represents a list of peoples' names +together with their email addresses and information about those people. The second data file, called @file{inventory-shipped}, contains information about monthly shipments. In both files, each line is considered to be one @dfn{record}. -In the data file @file{BBS-list}, each record contains the name of a computer -bulletin board, its phone number, the board's baud rate(s), and a code for -the number of hours it is operational. An @samp{A} in the last column -means the board operates 24 hours a day. A @samp{B} in the last -column means the board only operates on evening and weekend hours. -A @samp{C} means the board operates only on weekends: +In the data file @file{mail-list}, each record contains the name of a person, +his/her phone number, his/her email-address, and a code for their relationship +with the author of the list. An @samp{A} in the last column +means that the person is an acquaintance. An @samp{F} in the last +column means that the person is a friend. +An @samp{R} means that the person is a relative: -@c 2e: Update the baud rates to reflect today's faster modems @example @c system if test ! -d eg ; then mkdir eg ; fi @c system if test ! -d eg/lib ; then mkdir eg/lib ; fi @c system if test ! -d eg/data ; then mkdir eg/data ; fi @c system if test ! -d eg/prog ; then mkdir eg/prog ; fi @c system if test ! -d eg/misc ; then mkdir eg/misc ; fi -@c file eg/data/BBS-list -aardvark 555-5553 1200/300 B -alpo-net 555-3412 2400/1200/300 A -barfly 555-7685 1200/300 A -bites 555-1675 2400/1200/300 A -camelot 555-0542 300 C -core 555-2912 1200/300 C -fooey 555-1234 2400/1200/300 B -foot 555-6699 1200/300 B -macfoo 555-6480 1200/300 A -sdace 555-3430 2400/1200/300 A -sabafoo 555-2127 1200/300 C +@c file eg/data/mail-list +Amelia 555-5553 amelia.zodiacusque@@gmail.com F +Anthony 555-3412 anthony.asserturo@@hotmail.com A +Becky 555-7685 becky.algebrarum@@gmail.com A +Bill 555-1675 bill.drowning@@hotmail.com A +Broderick 555-0542 broderick.aliquotiens@@yahoo.com R +Camilla 555-2912 camilla.infusarum@@skynet.be R +Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +Julie 555-6699 julie.perscrutabor@@skeeve.com F +Martin 555-6480 martin.codicibus@@hotmail.com A +Samuel 555-3430 samuel.lanceolis@@shu.edu A +Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @c endfile @end example @@ -2558,23 +2557,23 @@ in the directory @file{awklib/eg/data}. @section Some Simple Examples The following command runs a simple @command{awk} program that searches the -input file @file{BBS-list} for the character string @samp{foo} (a +input file @file{mail-list} for the character string @samp{li} (a grouping of characters is usually called a @dfn{string}; the term @dfn{string} is based on similar usage in English, such as ``a string of pearls,'' or ``a string of cars in a train''): @example -awk '/foo/ @{ print $0 @}' BBS-list +awk '/li/ @{ print $0 @}' mail-list @end example @noindent -When lines containing @samp{foo} are found, they are printed because +When lines containing @samp{li} are found, they are printed because @w{@samp{print $0}} means print the current line. (Just @samp{print} by itself means the same thing, so we could have written that instead.) -You will notice that slashes (@samp{/}) surround the string @samp{foo} -in the @command{awk} program. The slashes indicate that @samp{foo} +You will notice that slashes (@samp{/}) surround the string @samp{li} +in the @command{awk} program. The slashes indicate that @samp{li} is the pattern to search for. This type of pattern is called a @dfn{regular expression}, which is covered in more detail later (@pxref{Regexp}). @@ -2586,11 +2585,11 @@ interpret any of it as special shell characters. Here is what this program prints: @example -$ @kbd{awk '/foo/ @{ print $0 @}' BBS-list} -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sabafoo 555-2127 1200/300 C +$ @kbd{awk '/li/ @{ print $0 @}' mail-list} +@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F +@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R +@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F +@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A @end example @cindex actions, default @@ -2603,7 +2602,7 @@ action is to print all lines that match the pattern. @cindex actions, empty Thus, we could leave out the action (the @code{print} statement and the curly braces) in the previous example and the result would be the same: -@command{awk} prints all lines matching the pattern @samp{foo}. By comparison, +@command{awk} prints all lines matching the pattern @samp{li}. By comparison, omitting the @code{print} statement but retaining the curly braces makes an empty action that does nothing (i.e., no lines are printed). @@ -2748,29 +2747,23 @@ This program prints every line that contains the string strings, it is printed twice, once by each rule. This is what happens if we run this program on our two sample data files, -@file{BBS-list} and @file{inventory-shipped}: +@file{mail-list} and @file{inventory-shipped}: @example $ @kbd{awk '/12/ @{ print $0 @}} -> @kbd{/21/ @{ print $0 @}' BBS-list inventory-shipped} -@print{} aardvark 555-5553 1200/300 B -@print{} alpo-net 555-3412 2400/1200/300 A -@print{} barfly 555-7685 1200/300 A -@print{} bites 555-1675 2400/1200/300 A -@print{} core 555-2912 1200/300 C -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sdace 555-3430 2400/1200/300 A -@print{} sabafoo 555-2127 1200/300 C -@print{} sabafoo 555-2127 1200/300 C +> @kbd{/21/ @{ print $0 @}' mail-list inventory-shipped} +@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A +@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R +@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @print{} Jan 21 36 64 620 @print{} Apr 21 70 74 514 @end example @noindent -Note how the line beginning with @samp{sabafoo} -in @file{BBS-list} was printed twice, once for each rule. +Note how the line beginning with @samp{Jean-Paul} +in @file{mail-list} was printed twice, once for each rule. @node More Complex @section A More Complex Example @@ -2849,7 +2842,7 @@ separate rule, like this: @example awk '/12/ @{ print $0 @} - /21/ @{ print $0 @}' BBS-list inventory-shipped + /21/ @{ print $0 @}' mail-list inventory-shipped @end example @cindex @command{gawk}, newlines in @@ -4259,14 +4252,14 @@ slashes. Then the regular expression is tested against the entire text of each record. (Normally, it only needs to match some part of the text in order to succeed.) For example, the following prints the second field of each record that contains the string -@samp{foo} anywhere in it: +@samp{li} anywhere in it: @example -$ @kbd{awk '/foo/ @{ print $2 @}' BBS-list} -@print{} 555-1234 +$ @kbd{awk '/li/ @{ print $2 @}' mail-list} +@print{} 555-5553 +@print{} 555-0542 @print{} 555-6699 -@print{} 555-6480 -@print{} 555-2127 +@print{} 555-3430 @end example @cindex regular expressions, operators @@ -5448,66 +5441,78 @@ For example: @cindex @code{BEGIN} pattern @example -awk 'BEGIN @{ RS = "/" @} - @{ print $0 @}' BBS-list +awk 'BEGIN @{ RS = "u" @} + @{ print $0 @}' mail-list @end example @noindent -changes the value of @code{RS} to @code{"/"}, before reading any input. -This is a string whose first character is a slash; as a result, records -are separated by slashes. Then the input file is read, and the second +changes the value of @code{RS} to @samp{u}, before reading any input. +This is a string whose first character is the letter ``u;'' as a result, records +are separated by the letter ``u.'' Then the input file is read, and the second rule in the @command{awk} program (the action with no pattern) prints each record. Because each @code{print} statement adds a newline at the end of its output, this @command{awk} program copies the input -with each slash changed to a newline. Here are the results of running -the program on @file{BBS-list}: - -@example -$ @kbd{awk 'BEGIN @{ RS = "/" @}} -> @kbd{@{ print $0 @}' BBS-list} -@print{} aardvark 555-5553 1200 -@print{} 300 B -@print{} alpo-net 555-3412 2400 -@print{} 1200 -@print{} 300 A -@print{} barfly 555-7685 1200 -@print{} 300 A -@print{} bites 555-1675 2400 -@print{} 1200 -@print{} 300 A -@print{} camelot 555-0542 300 C -@print{} core 555-2912 1200 -@print{} 300 C -@print{} fooey 555-1234 2400 -@print{} 1200 -@print{} 300 B -@print{} foot 555-6699 1200 -@print{} 300 B -@print{} macfoo 555-6480 1200 -@print{} 300 A -@print{} sdace 555-3430 2400 -@print{} 1200 -@print{} 300 A -@print{} sabafoo 555-2127 1200 -@print{} 300 C -@print{} +with each @samp{u} changed to a newline. Here are the results of running +the program on @file{mail-list}: + +@example +$ @kbd{awk 'BEGIN @{ RS = "u" @}} +> @kbd{@{ print $0 @}' mail-list} +@print{} Amelia 555-5553 amelia.zodiac +@print{} sq +@print{} e@@gmail.com F +@print{} Anthony 555-3412 anthony.assert +@print{} ro@@hotmail.com A +@print{} Becky 555-7685 becky.algebrar +@print{} m@@gmail.com A +@print{} Bill 555-1675 bill.drowning@@hotmail.com A +@print{} Broderick 555-0542 broderick.aliq +@print{} otiens@@yahoo.com R +@print{} Camilla 555-2912 camilla.inf +@print{} sar +@print{} m@@skynet.be R +@print{} Fabi +@print{} s 555-1234 fabi +@print{} s. +@print{} ndevicesim +@print{} s@@ +@print{} cb.ed +@print{} F +@print{} J +@print{} lie 555-6699 j +@print{} lie.perscr +@print{} tabor@@skeeve.com F +@print{} Martin 555-6480 martin.codicib +@print{} s@@hotmail.com A +@print{} Sam +@print{} el 555-3430 sam +@print{} el.lanceolis@@sh +@print{} .ed +@print{} A +@print{} Jean-Pa +@print{} l 555-2127 jeanpa +@print{} l.campanor +@print{} m@@ny +@print{} .ed +@print{} R +@print{} @end example @noindent -Note that the entry for the @samp{camelot} BBS is not split. +Note that the entry for the name @samp{Bill} is not split. In the original data file (@pxref{Sample Data Files}), the line looks like this: @example -camelot 555-0542 300 C +Bill 555-1675 bill.drowning@@hotmail.com A @end example @noindent -It has one baud rate only, so there are no slashes in the record, -unlike the others which have two or more baud rates. -In fact, this record is treated as part of the record -for the @samp{core} BBS; the newline separating them in the output +It contains no @samp{u} so there is no reason to split the record, +unlike the others which have one or more occurrences of the @samp{u}. +In fact, this record is treated as part of the previous record; +the newline separating them in the output is the original newline in the data file, not the one added by @command{awk} when it printed the record! @@ -5518,14 +5523,17 @@ using the variable-assignment feature (@pxref{Other Arguments}): @example -awk '@{ print $0 @}' RS="/" BBS-list +awk '@{ print $0 @}' RS="u" mail-list @end example @noindent -This sets @code{RS} to @samp{/} before processing @file{BBS-list}. +This sets @code{RS} to @samp{u} before processing @file{mail-list}. -Using an unusual character such as @samp{/} for the record separator -produces correct behavior in the vast majority of cases. +Using an alphabetic character such as @samp{u} for the record separator +is highly likely to produce strange results. +Using an unusual character such as @samp{/} is more likely to +produce correct behavior in the majority of cases, but there +are no guarantees. The moral is: Know Your Data. There is one unusual case, that occurs when @command{gawk} is being fully POSIX-compliant (@pxref{Options}). @@ -5755,31 +5763,29 @@ when you are not interested in specific fields. Here are some more examples: @example -$ @kbd{awk '$1 ~ /foo/ @{ print $0 @}' BBS-list} -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sabafoo 555-2127 1200/300 C +$ @kbd{awk '$1 ~ /li/ @{ print $0 @}' mail-list} +@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F +@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F @end example @noindent -This example prints each record in the file @file{BBS-list} whose first -field contains the string @samp{foo}. The operator @samp{~} is called a +This example prints each record in the file @file{mail-list} whose first +field contains the string @samp{li}. The operator @samp{~} is called a @dfn{matching operator} (@pxref{Regexp Usage}); it tests whether a string (here, the field @code{$1}) matches a given regular expression. By contrast, the following example -looks for @samp{foo} in @emph{the entire record} and prints the first +looks for @samp{li} in @emph{the entire record} and prints the first field and the last field for each matching input record: @example -$ @kbd{awk '/foo/ @{ print $1, $NF @}' BBS-list} -@print{} fooey B -@print{} foot B -@print{} macfoo A -@print{} sabafoo C +$ @kbd{awk '/li/ @{ print $1, $NF @}' mail-list} +@print{} Amelia F +@print{} Broderick R +@print{} Julie F +@print{} Samuel A @end example @c ENDOFRANGE fiex @@ -5807,7 +5813,7 @@ the record has fewer than 20 fields, so this prints a blank line. Here is another example of using expressions as field numbers: @example -awk '@{ print $(2*2) @}' BBS-list +awk '@{ print $(2*2) @}' mail-list @end example @command{awk} evaluates the expression @samp{(2*2)} and uses @@ -5816,8 +5822,8 @@ represents multiplication, so the expression @samp{2*2} evaluates to four. The parentheses are used so that the multiplication is done before the @samp{$} operation; they are necessary whenever there is a binary operator in the field-number expression. This example, then, prints the -hours of operation (the fourth field) for every line of the file -@file{BBS-list}. (All of the @command{awk} operators are listed, in +type of relationship (the fourth field) for every line of the file +@file{mail-list}. (All of the @command{awk} operators are listed, in order of decreasing precedence, in @ref{Precedence}.) @@ -6348,66 +6354,59 @@ figures that you really want your fields to be separated with TABs and not @samp{t}s. Use @samp{-v FS="t"} or @samp{-F"[t]"} on the command line if you really do want to separate your fields with @samp{t}s. -As an example, let's use an @command{awk} program file called @file{baud.awk} -that contains the pattern @code{/300/} and the action @samp{print $1}: +As an example, let's use an @command{awk} program file called @file{edu.awk} +that contains the pattern @code{/edu/} and the action @samp{print $1}: @example -/300/ @{ print $1 @} +/edu/ @{ print $1 @} @end example Let's also set @code{FS} to be the @samp{-} character and run the -program on the file @file{BBS-list}. The following command prints a -list of the names of the bulletin boards that operate at 300 baud and +program on the file @file{mail-list}. The following command prints a +list of the names of the people that work at or attend a university, and the first three digits of their phone numbers: @c tweaked to make the tex output look better in @smallbook @example -$ @kbd{awk -F- -f baud.awk BBS-list} -@print{} aardvark 555 -@print{} alpo -@print{} barfly 555 -@print{} bites 555 -@print{} camelot 555 -@print{} core 555 -@print{} fooey 555 -@print{} foot 555 -@print{} macfoo 555 -@print{} sdace 555 -@print{} sabafoo 555 +$ @kbd{awk -F- -f edu.awk mail-list} +@print{} Fabius 555 +@print{} Samuel 555 +@print{} Jean @end example @noindent -Note the second line of output. The second line +Note the third line of output. The third line in the original file looked like this: @example -alpo-net 555-3412 2400/1200/300 A +Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @end example -The @samp{-} as part of the system's name was used as the field +The @samp{-} as part of the person's name was used as the field separator, instead of the @samp{-} in the phone number that was originally intended. This demonstrates why you have to be careful in choosing your field and record separators. @cindex Unix @command{awk}, password files@comma{} field separators and -Perhaps the most common use of a single character as the field -separator occurs when processing the Unix system password file. -On many Unix systems, each user has a separate entry in the system password -file, one line per user. The information in these lines is separated -by colons. The first field is the user's login name and the second is -the user's (encrypted or shadow) password. A password file entry might look -like this: +Perhaps the most common use of a single character as the field separator +occurs when processing the Unix system password file. On many Unix +systems, each user has a separate entry in the system password file, one +line per user. The information in these lines is separated by colons. +The first field is the user's login name and the second is the user's +encrypted or shadow password. (A shadow password is indicated by the +presence of a single @samp{x} in the second field.) A password file +entry might look like this: @cindex Robbins, Arnold @example -arnold:xyzzy:2076:10:Arnold Robbins:/home/arnold:/bin/bash +arnold:x:2076:10:Arnold Robbins:/home/arnold:/bin/bash @end example The following program searches the system password file and prints -the entries for users who have no password: +the entries for users whose full name is not indicated: @example -awk -F: '$2 == ""' /etc/passwd +awk -F: '$5 == ""' /etc/passwd @end example @node Full Line Fields @@ -7883,13 +7882,29 @@ program by using a new value of @code{OFS}. @example $ @kbd{awk 'BEGIN @{ OFS = ";"; ORS = "\n\n" @}} -> @kbd{@{ print $1, $2 @}' BBS-list} -@print{} aardvark;555-5553 -@print{} -@print{} alpo-net;555-3412 -@print{} -@print{} barfly;555-7685 -@dots{} +> @kbd{@{ print $1, $2 @}' mail-list} +@print{} Amelia;555-5553 +@print{} +@print{} Anthony;555-3412 +@print{} +@print{} Becky;555-7685 +@print{} +@print{} Bill;555-1675 +@print{} +@print{} Broderick;555-0542 +@print{} +@print{} Camilla;555-2912 +@print{} +@print{} Fabius;555-1234 +@print{} +@print{} Julie;555-6699 +@print{} +@print{} Martin;555-6480 +@print{} +@print{} Samuel;555-3430 +@print{} +@print{} Jean-Paul;555-2127 +@print{} @end example If the value of @code{ORS} does not contain a newline, the program's output @@ -8363,30 +8378,30 @@ The following simple example shows how to use @code{printf} to make an aligned table: @example -awk '@{ printf "%-10s %s\n", $1, $2 @}' BBS-list +awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list @end example @noindent This command -prints the names of the bulletin boards (@code{$1}) in the file -@file{BBS-list} as a string of 10 characters that are left-justified. It also +prints the names of the people (@code{$1}) in the file +@file{mail-list} as a string of 10 characters that are left-justified. It also prints the phone numbers (@code{$2}) next on the line. This produces an aligned two-column table of names and phone numbers, as shown here: @example -$ @kbd{awk '@{ printf "%-10s %s\n", $1, $2 @}' BBS-list} -@print{} aardvark 555-5553 -@print{} alpo-net 555-3412 -@print{} barfly 555-7685 -@print{} bites 555-1675 -@print{} camelot 555-0542 -@print{} core 555-2912 -@print{} fooey 555-1234 -@print{} foot 555-6699 -@print{} macfoo 555-6480 -@print{} sdace 555-3430 -@print{} sabafoo 555-2127 +$ @kbd{awk '@{ printf "%-10s %s\n", $1, $2 @}' mail-list} +@print{} Amelia 555-5553 +@print{} Anthony 555-3412 +@print{} Becky 555-7685 +@print{} Bill 555-1675 +@print{} Broderick 555-0542 +@print{} Camilla 555-2912 +@print{} Fabius 555-1234 +@print{} Julie 555-6699 +@print{} Martin 555-6480 +@print{} Samuel 555-3430 +@print{} Jean-Paul 555-2127 @end example In this case, the phone numbers had to be printed as strings because @@ -8407,7 +8422,7 @@ the @command{awk} program: @example awk 'BEGIN @{ print "Name Number" print "---- ------" @} - @{ printf "%-10s %s\n", $1, $2 @}' BBS-list + @{ printf "%-10s %s\n", $1, $2 @}' mail-list @end example The above example mixes @code{print} and @code{printf} statements in @@ -8417,7 +8432,7 @@ same results: @example awk 'BEGIN @{ printf "%-10s %s\n", "Name", "Number" printf "%-10s %s\n", "----", "------" @} - @{ printf "%-10s %s\n", $1, $2 @}' BBS-list + @{ printf "%-10s %s\n", $1, $2 @}' mail-list @end example @noindent @@ -8432,7 +8447,7 @@ emphasized by storing it in a variable, like this: awk 'BEGIN @{ format = "%-10s %s\n" printf format, "Name", "Number" printf format, "----", "------" @} - @{ printf format, $1, $2 @}' BBS-list + @{ printf format, $1, $2 @}' mail-list @end example @c !!! exercise @@ -8489,20 +8504,20 @@ before the first output is written to it. Subsequent writes to the same @var{output-file} do not erase @var{output-file}, but append to it. (This is different from how you use redirections in shell scripts.) If @var{output-file} does not exist, it is created. For example, here -is how an @command{awk} program can write a list of BBS names to one +is how an @command{awk} program can write a list of peoples' names to one file named @file{name-list}, and a list of phone numbers to another file named @file{phone-list}: @example $ @kbd{awk '@{ print $2 > "phone-list"} -> @kbd{print $1 > "name-list" @}' BBS-list} +> @kbd{print $1 > "name-list" @}' mail-list} $ @kbd{cat phone-list} @print{} 555-5553 @print{} 555-3412 @dots{} $ @kbd{cat name-list} -@print{} aardvark -@print{} alpo-net +@print{} Amelia +@print{} Anthony @dots{} @end example @@ -8531,7 +8546,7 @@ to another process created to execute @var{command}. The redirection argument @var{command} is actually an @command{awk} expression. Its value is converted to a string whose contents give the shell command to be run. For example, the following produces two -files, one unsorted list of BBS names, and one list sorted in reverse +files, one unsorted list of peoples' names, and one list sorted in reverse alphabetical order: @ignore @@ -8544,7 +8559,7 @@ alone for now and let's hope no-one notices. @example awk '@{ print $1 > "names.unsorted" command = "sort -r > names.sorted" - print $1 | command @}' BBS-list + print $1 | command @}' mail-list @end example The unsorted list is written with an ordinary redirection, while @@ -9486,7 +9501,7 @@ its position among the input file arguments---after the processing of the preceding input file argument. For example: @example -awk '@{ print $n @}' n=4 inventory-shipped n=2 BBS-list +awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list @end example @noindent @@ -9495,10 +9510,10 @@ the first file is read, the command line sets the variable @code{n} equal to four. This causes the fourth field to be printed in lines from @file{inventory-shipped}. After the first file has finished, but before the second file is started, @code{n} is set to two, so that the -second field is printed in lines from @file{BBS-list}: +second field is printed in lines from @file{mail-list}: @example -$ @kbd{awk '@{ print $n @}' n=4 inventory-shipped n=2 BBS-list} +$ @kbd{awk '@{ print $n @}' n=4 inventory-shipped n=2 mail-list} @print{} 15 @print{} 24 @dots{} @@ -9821,9 +9836,9 @@ specific operator to represent it. Instead, concatenation is performed by writing expressions next to one another, with no operator. For example: @example -$ @kbd{awk '@{ print "Field number one: " $1 @}' BBS-list} -@print{} Field number one: aardvark -@print{} Field number one: alpo-net +$ @kbd{awk '@{ print "Field number one: " $1 @}' mail-list} +@print{} Field number one: Amelia +@print{} Field number one: Anthony @dots{} @end example @@ -9831,9 +9846,9 @@ Without the space in the string constant after the @samp{:}, the line runs together. For example: @example -$ @kbd{awk '@{ print "Field number one:" $1 @}' BBS-list} -@print{} Field number one:aardvark -@print{} Field number one:alpo-net +$ @kbd{awk '@{ print "Field number one:" $1 @}' mail-list} +@print{} Field number one:Amelia +@print{} Field number one:Anthony @dots{} @end example @@ -10796,10 +10811,10 @@ The Boolean operators are: @item @var{boolean1} && @var{boolean2} True if both @var{boolean1} and @var{boolean2} are true. For example, the following statement prints the current input record if it contains -both @samp{2400} and @samp{foo}: +both @samp{edu} and @samp{li}: @example -if ($0 ~ /2400/ && $0 ~ /foo/) print +if ($0 ~ /edu/ && $0 ~ /li/) print @end example @cindex side effects, Boolean operators @@ -10812,11 +10827,11 @@ no substring @samp{foo} in the record. @item @var{boolean1} || @var{boolean2} True if at least one of @var{boolean1} or @var{boolean2} is true. For example, the following statement prints all records in the input -that contain @emph{either} @samp{2400} or -@samp{foo} or both: +that contain @emph{either} @samp{edu} or +@samp{li} or both: @example -if ($0 ~ /2400/ || $0 ~ /foo/) print +if ($0 ~ /edu/ || $0 ~ /li/) print @end example The subexpression @var{boolean2} is evaluated only if @var{boolean1} @@ -11411,7 +11426,7 @@ slashes (@code{/@var{regexp}/}), or any expression whose string value is used as a dynamic regular expression (@pxref{Computed Regexps}). The following example prints the second field of each input record -whose first field is precisely @samp{foo}: +whose first field is precisely @samp{li}: @cindex @code{/} (forward slash), patterns and @cindex forward slash (@code{/}), patterns and @@ -11420,68 +11435,65 @@ whose first field is precisely @samp{foo}: @cindex @code{!} (exclamation point), @code{!~} operator @cindex exclamation point (@code{!}), @code{!~} operator @example -$ @kbd{awk '$1 == "foo" @{ print $2 @}' BBS-list} +$ @kbd{awk '$1 == "li" @{ print $2 @}' mail-list} @end example @noindent -(There is no output, because there is no BBS site with the exact name @samp{foo}.) +(There is no output, because there is no person with the exact name @samp{li}.) Contrast this with the following regular expression match, which -accepts any record with a first field that contains @samp{foo}: +accepts any record with a first field that contains @samp{li}: @example -$ @kbd{awk '$1 ~ /foo/ @{ print $2 @}' BBS-list} -@print{} 555-1234 +$ @kbd{awk '$1 ~ /foo/ @{ print $2 @}' mail-list} +@print{} 555-5553 @print{} 555-6699 -@print{} 555-6480 -@print{} 555-2127 @end example @cindex regexp constants, as patterns @cindex patterns, regexp constants as A regexp constant as a pattern is also a special case of an expression -pattern. The expression @code{/foo/} has the value one if @samp{foo} -appears in the current input record. Thus, as a pattern, @code{/foo/} -matches any record containing @samp{foo}. +pattern. The expression @code{/li/} has the value one if @samp{li} +appears in the current input record. Thus, as a pattern, @code{/li/} +matches any record containing @samp{li}. @cindex Boolean expressions, as patterns Boolean expressions are also commonly used as patterns. Whether the pattern matches an input record depends on whether its subexpressions match. For example, the following command prints all the records in -@file{BBS-list} that contain both @samp{2400} and @samp{foo}: +@file{mail-list} that contain both @samp{edu} and @samp{li}: @example -$ @kbd{awk '/2400/ && /foo/' BBS-list} -@print{} fooey 555-1234 2400/1200/300 B +$ @kbd{awk '/edu/ && /li/' mail-list} +@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A @end example The following command prints all records in -@file{BBS-list} that contain @emph{either} @samp{2400} or @samp{foo} +@file{mail-list} that contain @emph{either} @samp{edu} or @samp{li} (or both, of course): @example -$ @kbd{awk '/2400/ || /foo/' BBS-list} -@print{} alpo-net 555-3412 2400/1200/300 A -@print{} bites 555-1675 2400/1200/300 A -@print{} fooey 555-1234 2400/1200/300 B -@print{} foot 555-6699 1200/300 B -@print{} macfoo 555-6480 1200/300 A -@print{} sdace 555-3430 2400/1200/300 A -@print{} sabafoo 555-2127 1200/300 C +$ @kbd{awk '/edu/ || /li/' mail-list} +@print{} Amelia 555-5553 amelia.zodiacusque@@gmail.com F +@print{} Broderick 555-0542 broderick.aliquotiens@@yahoo.com R +@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +@print{} Julie 555-6699 julie.perscrutabor@@skeeve.com F +@print{} Samuel 555-3430 samuel.lanceolis@@shu.edu A +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @end example The following command prints all records in -@file{BBS-list} that do @emph{not} contain the string @samp{foo}: +@file{mail-list} that do @emph{not} contain the string @samp{li}: @example -$ @kbd{awk '! /foo/' BBS-list} -@print{} aardvark 555-5553 1200/300 B -@print{} alpo-net 555-3412 2400/1200/300 A -@print{} barfly 555-7685 1200/300 A -@print{} bites 555-1675 2400/1200/300 A -@print{} camelot 555-0542 300 C -@print{} core 555-2912 1200/300 C -@print{} sdace 555-3430 2400/1200/300 A +$ @kbd{awk '! /li/' mail-list} +@print{} Anthony 555-3412 anthony.asserturo@@hotmail.com A +@print{} Becky 555-7685 becky.algebrarum@@gmail.com A +@print{} Bill 555-1675 bill.drowning@@hotmail.com A +@print{} Camilla 555-2912 camilla.infusarum@@skynet.be R +@print{} Fabius 555-1234 fabius.undevicesimus@@ucb.edu F +@print{} Martin 555-6480 martin.codicibus@@hotmail.com A +@print{} Jean-Paul 555-2127 jeanpaul.campanorum@@nyu.edu R @end example @cindex @code{BEGIN} pattern, Boolean patterns and @@ -11620,22 +11632,22 @@ input is read. For example: @example $ @kbd{awk '} -> @kbd{BEGIN @{ print "Analysis of \"foo\"" @}} -> @kbd{/foo/ @{ ++n @}} -> @kbd{END @{ print "\"foo\" appears", n, "times." @}' BBS-list} -@print{} Analysis of "foo" -@print{} "foo" appears 4 times. +> @kbd{BEGIN @{ print "Analysis of \"li\"" @}} +> @kbd{/li/ @{ ++n @}} +> @kbd{END @{ print "\"li\" appears in", n, "records." @}' mail-list} +@print{} Analysis of "li" +@print{} "li" appears in 4 records. @end example @cindex @code{BEGIN} pattern, operators and @cindex @code{END} pattern, operators and -This program finds the number of records in the input file @file{BBS-list} -that contain the string @samp{foo}. The @code{BEGIN} rule prints a title +This program finds the number of records in the input file @file{mail-list} +that contain the string @samp{li}. The @code{BEGIN} rule prints a title for the report. There is no need to use the @code{BEGIN} rule to initialize the counter @code{n} to zero, since @command{awk} does this automatically (@pxref{Variables}). The second rule increments the variable @code{n} every time a -record containing the pattern @samp{foo} is read. The @code{END} rule +record containing the pattern @samp{li} is read. The @code{END} rule prints the value of @code{n} at the end of the run. The special patterns @code{BEGIN} and @code{END} cannot be used in ranges @@ -11799,7 +11811,7 @@ both @code{BEGINFILE} and @code{ENDFILE}. Only the @samp{getline In most other @command{awk} implementations, or if @command{gawk} is in compatibility mode (@pxref{Options}), they are not special. -@c FIXME: For 4.1 maybe deal with this? +@c FIXME: For 4.2 maybe deal with this? @ignore Date: Tue, 17 May 2011 02:06:10 PDT From: rankin@pactechdata.com (Pat Rankin) @@ -11830,7 +11842,7 @@ An empty (i.e., nonexistent) pattern is considered to match @emph{every} input record. For example, the program: @example -awk '@{ print $1 @}' BBS-list +awk '@{ print $1 @}' mail-list @end example @noindent @@ -13032,16 +13044,16 @@ In the following example: $ @kbd{awk 'BEGIN @{} > @kbd{for (i = 0; i < ARGC; i++)} > @kbd{print ARGV[i]} -> @kbd{@}' inventory-shipped BBS-list} +> @kbd{@}' inventory-shipped mail-list} @print{} awk @print{} inventory-shipped -@print{} BBS-list +@print{} mail-list @end example @noindent @code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]} contains @samp{inventory-shipped}, and @code{ARGV[2]} contains -@samp{BBS-list}. The value of @code{ARGC} is three, one more than the +@samp{mail-list}. The value of @code{ARGC} is three, one more than the index of the last element in @code{ARGV}, because the elements are numbered from zero. @@ -13462,16 +13474,16 @@ and @code{ARGV}: $ @kbd{awk 'BEGIN @{} > @kbd{for (i = 0; i < ARGC; i++)} > @kbd{print ARGV[i]} -> @kbd{@}' inventory-shipped BBS-list} +> @kbd{@}' inventory-shipped mail-list} @print{} awk @print{} inventory-shipped -@print{} BBS-list +@print{} mail-list @end example @noindent In this example, @code{ARGV[0]} contains @samp{awk}, @code{ARGV[1]} contains @samp{inventory-shipped}, and @code{ARGV[2]} contains -@samp{BBS-list}. +@samp{mail-list}. Notice that the @command{awk} program is not entered in @code{ARGV}. The other command-line options, with their arguments, are also not entered. This includes variable assignments done with the @option{-v} @@ -33885,6 +33897,11 @@ Arnold Robbins and Andrew Schorr, with notable contributions from the rest of the development team. @item +@cindex Colombo, Antonio +Antonio Giovanni Colombo rewrote a number of examples in the early +chapters that were severely dated, for which I am incredibly grateful. + +@item @cindex Robbins, Arnold Arnold Robbins has been working on @command{gawk} since 1988, at first @@ -36625,9 +36642,6 @@ The GNU version of the standard shell @end ifinfo See also ``Bourne Shell.'' -@item BBS -See ``Bulletin Board System.'' - @item Bit Short for ``Binary Digit.'' All values in computer memory ultimately reduce to binary digits: values @@ -36702,11 +36716,6 @@ Changing some of them affects @command{awk}'s running environment. @item Braces See ``Curly Braces.'' -@item Bulletin Board System -A computer system allowing users to log in and read and/or leave messages -for other users of the system, much like leaving paper notes on a bulletin -board. - @item C The system programming language that most GNU software is written in. The @command{awk} programming language has C-like syntax, and this @value{DOCUMENT} @@ -38672,8 +38681,6 @@ Suggestions: % Next edition: % 1. Standardize the error messages from the functions and programs % in the two sample code chapters. -% 2. Nuke the BBS stuff and use something that won't be obsolete -% 3. Turn the advanced notes into sidebars by using @cartouche Better sidebars can almost sort of be done with: @@ -38705,4 +38712,3 @@ But to use it you have to say } which sorta sucks. - |