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asprintf

Section: C Library Functions (3)
Updated: 202-0-08
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NAME

asprintf, vasprintf - print to allocated string

LIBRARY

Standard C library (libc,~-lc)

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 ([aq][rs]0[aq]), 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). On error, -1 is returned, errno is set to indicate the error, and the contents of strp are undefined.

ERRORS

See sprintf(3) and malloc(3).

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
asprintf(), vasprintf()	Thread safety	M-Safe locale

VERSIONS

The FreeBSD implementation sets strp to NULL on error.

STANDARDS

GNU, BSD.