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ASPRINTF(3) Linux Programmer's Manual ASPRINTF(3)
NAME
asprintf, vasprintf - print to allocated string
SYNOPSIS
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <stdio.h>
int asprintf(char **restrict strp, const char *restrict fmt, ...);
int vasprintf(char **restrict strp, const char *restrict fmt,
va_list ap);
DESCRIPTION
The functions asprintf() and vasprintf() are analogs of sprintf(3) and vsprintf(3), except that they allocate a string large enough to hold the output including
the terminating null byte ('\0'), and return a pointer to it via the first argument. 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 are undefined.
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┼───────────────┼────────────────┤
│asprintf(), vasprintf() │ Thread safety │ MT-Safe locale │
└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘
CONFORMING TO
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 2021-03-22 ASPRINTF(3)