redhat man page for asprintf

ASPRINTF(3)						     Linux Programmer's Manual						       ASPRINTF(3)

NAME
       asprintf, vasprintf - print to allocated string

SYNOPSIS
       #define _GNU_SOURCE
       #include <stdio.h>

       int asprintf(char **strp, const char *fmt, ...);

       int vasprintf(char **strp, const char *fmt, va_list ap);

DESCRIPTION
       The  functions  asprintf  and  vasprintf are analogues of sprintf and vsprintf, except that they allocate a string large enough to hold the
       output including the terminating NUL, and return a pointer to it via the first parameter.  This pointer should  be  passed  to  free(3)	to
       release the allocated storage when it is no longer needed.

RETURN VALUE
       When  successful,  these functions return the number of bytes printed, just like sprintf(3).  If memory allocation wasn't possible, or some
       other error occurs, these functions will return -1, and the contents of strp is undefined.

NOTES
       These functions are GNU extensions, not in C or POSIX.  They are also available under *BSD.  The FreeBSD implementation sets strp  to  NULL
       on error.

SEE ALSO
       free(3), malloc(3), printf(3)

GNU
								    2001-12-18							       ASPRINTF(3)