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.. SPDX-License-Identifier: GPL-2.0+
setexpr command
===============
Synopsis
--------
::
setexpr[.b, .w, .l .s] <name> [*]<value> <op> [*]<value2>
setexpr[.b, .w, .l] <name> [*]<value>
setexpr <name> fmt <format> [value]...
setexpr <name> gsub r s [t]
setexpr <name> sub r s [t]
Description
-----------
The setexpr command is used to set an environment variable to the result
of an evaluation.
setexpr[.b, .w, .l .s] <name> [*]<value> <op> [*]<value2>
Set environment variable <name> to the result of the evaluated
expression specified by <op>.
setexpr[.b, .w, .l] name [*]value
Load <value> into environment variable <name>
setexpr name fmt <format> value
Set environment variable <name> to the result of the C like
format string <format> evaluation of <value>.
setexpr name gsub <r> <s> [<t>]
For each substring matching the regular expression <r> in the
string <t>, substitute the string <s>.
The result is assigned to <name>.
If <t> is not supplied, use the old value of <name>.
setexpr name sub <r> <s> [<t>]
Just like gsub(), but replace only the first matching substring
The setexpr command takes the following arguments:
format
This parameter contains a C or Bash like format string.
The number of arguments is limited to 4.
The following format types are supported:
c
single character
d, i
decimal value
o
octal value
s
string
u
unsigned decimal value
x, X
hexadecimal value
'%'
no conversion, instead a % character will be written
Backslash escapes:
\" = double quote
\\ = backslash
\a = alert (bell)
\b = backspace
\c = produce no further output
\f = form feed
\n = new line
\r = carriage return
\t = horizontal tab
\v = vertical tab
\NNN = octal number (NNN is 0 to 3 digits)
name
The name of the environment variable to be set
op
'|'
name = value | value2
'&'
name = value & value2
'+'
name = value + value2
(This is the only operator supported for strings.
It acts as concatenation operator on strings)
'^'
name = value ^ value2
'-'
name = value - value2
'*'
name = value * value2
'/'
name = value / value2
'%'
name = value % value2
r
Regular expression
s
Substitution string
t
string
value
Can either be an integer value, a string.
If the pointer prefix '*' is given value is treated as memory address.
value2
See value
Example
-------
::
=> setexpr foo fmt %d 0x100
=> echo $foo
256
=>
=> setexpr foo fmt 0x%08x 63
=> echo $foo
0x00000063
=>
=> setexpr foo fmt %%%o 8
=> echo $foo
%10
=>
Configuration
-------------
* The *setexpr* command is only available if CMD_SETEXPR=y.
* The *setexpr fmt* sub-command is only available if CMD_SETEXPR_FMT=y.
* The *setexpr gsub* and *setexpr sub* sub-commands are only available if
CONFIG_REGEX=y.
Return value
------------
The return value $? is set to 0 (true) if the operation was successful.
If an error occurs, the return value $? is set to 1 (false).
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