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@node snprintfv
@section Replacement for Stdio Formatting Library
Using the `printf' formatting routines in a portable fashion has
always been a pain, and this package has been way more pain than anyone
ever imagined. Hopefully, with this release of snprintfv, the pain is
now over for all time.
The issues with portable usage are these:
@enumerate
@item
Argument number specifiers are often either not implemented or are
buggy. Even GNU libc, version 1 got it wrong.
@item
ANSI/ISO "forgot" to provide a mechanism for computing argument
lists for vararg procedures.
@item
The argument array version of printf (`printfv()') is not
generally available, does not work with the native printf, and
does not have a working argument number specifier in the format
specification. (Last I knew, anyway.)
@item
You cannot fake varargs by calling `vprintf()' with an array of
arguments, because ANSI does not require such an implementation
and some vendors play funny tricks because they are allowed to.
@end enumerate
These four issues made it impossible for AutoGen to ship without its
own implementation of the `printf' formatting routines. Since we were
forced to do this, we decided to make the formatting routines both
better and more complete :-). We addressed these issues and added the
following features to the common printf API:
@enumerate 5
@item
The formatted output can be written to
@itemize @bullet
@item
a string allocated by the formatting function (`asprintf()').
@item
a file descriptor instead of a file stream (`dprintf()').
@item
a user specified stream (`stream_printf()').
@end itemize
@item
The formatting functions can be augmented with your own functions.
These functions are allowed to consume more than one character
from the format, but must commence with a unique character. For
example,
@example
"%@{struct stat@}\n"
@end example
might be used with '@{' registered to a procedure that would look
up "struct stat" in a symbol table and do appropriate things,
consuming the format string through the '@}' character.
@end enumerate
Gary V. Vaughan was generous enough to supply this implementation.
Many thanks!!
For further details, the reader is referred to the snprintfv
documentation. These functions are also available in the template
processing as@: `sprintf' (@pxref{SCM sprintf}), `printf'
(@pxref{SCM printf}), `fprintf' (@pxref{SCM fprintf}), and `shellf'
(@pxref{SCM shellf}).
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