.\" Copyright (c) 2012 Thibault Meyer (thibault.meyer@xxxxxxxxxx)
.\"
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.TH REGISTER_PRINTF_SPECIFIER 3 2011-12-08 "GNU" "Linux Programmer's Manual"
.SH NAME
register_printf_specifier \- Add new format specifier to printf function
.SH SYNOPSIS
.B #include <printf.h>
.sp
.BI "typedef int printf_function (FILE *"stream ",struct printf_info
*" info ", void **"args ");"
.br
.BI "typedef int printf_arginfo_size_function (struct printf_info *"
info ", size_t "n ", int *"argtype ");"
.sp
.sp
.BI "int register_printf_specifier (int "spec ", printf_function "fct
", printf_arginfo_size_function "arginfo ");"
.sp
.SH DESCRIPTION
The function
.BR register_printf_specifier ()
allow developer to extend functionalities of
.BR printf ()
by registering new conversion format
.IR specifier .
Also you can redefine the standard output conversions specifier, but
this is not a good idea.
.SS Parameters
-
.IR spec
is the specifier that you like to implement on printf-family function.
If the specifier is 'B', it defines the conversion '%B'.
.br
-
.IR fct
represent the handler-function called by printf-family functions when
your defined
.IR spec
was found in format string.
.br
-
.IR arginfo
is the function called by
.BR parse_printf_format ()
when your defined
.IR spec
was found in format string.
.SS Return value
The function
.BR register_printf_specifier ()
return
.BR 0
on success and
.BR -1
if an error is encountered.
.sp
.SH BASIC EXAMPLE
Below you can found an basic example how to use
register_printf_specifier() function to implement the 'b' specifier to
allow binary output conversion.
.SS Code
#include <printf.h>
int my_binary_info(const struct printf_info* info __attribute__
((unused)), size_t n, int* argtype, int* size __attribute__
((unused)))
.br
{}
int my_binary(FILE *stream, const struct printf_info *info, const void
*const *args)
.br
{}
int main(void)
.br
{
.br
register_printf_specifier('b', my_binary, my_binary_info);
.br
printf("binary: %ld -> %b\n", 65536, 65536);
.br
printf("binary: %ld -> %b\n", 42, 42);
.br
printf("binary: %ld -> %b\n", 2, 2);
.br
return (0);
.br
}
.sp
.SH COLOPHON
This page is part of release 3.27 of the Linux
.IR man-pages
project. A description of the project, and information about
reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
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