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asprintf
<html> <head> <title>asprintf</title> <META NAME="KEYWORDS" CONTENT="asprintf"> </head> <body BGCOLOR="#ffffff" LINK="#0000ff" VLINK="#0000ff" ALINK="#0000ff" TEXT="#000000"> <center> <h1><b>asprintf</b></h1></center> <PRE> <STRONG><A HREF="/man3/ASPRINTF">ASPRINTF(3)</A></STRONG> Linux Programmer's Manual <STRONG><A HREF="/man3/ASPRINTF">ASPRINTF(3)</A></STRONG> NAME asprintf, vasprintf - print to allocated string SYNOPSIS #define _GNU_SOURCE /* See <STRONG><A HREF="/man7/feature_test_macros">feature_test_macros(7)</A></STRONG> */ #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 analogs of <STRONG><A HREF="/man3/sprintf">sprintf(3)</A></STRONG> and <STRONG><A HREF="/man3/vsprintf">vsprintf(3)</A></STRONG>, 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 <STRONG><A HREF="/man3/free">free(3)</A></STRONG> 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 <STRONG><A HREF="/man3/sprintf">sprintf(3)</A></STRONG>. 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 at- <STRONG><A HREF="/man7/tributes">tributes(7)</A></STRONG>. +------------------------+---------------+----------------+ |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 <STRONG><A HREF="/man3/free">free(3)</A></STRONG>, <STRONG><A HREF="/man3/malloc">malloc(3)</A></STRONG>, <STRONG><A HREF="/man3/printf">printf(3)</A></STRONG> COLOPHON This page is part of release 5.05 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/. GNU 2019-03-06 <STRONG><A HREF="/man3/ASPRINTF">ASPRINTF(3)</A></STRONG></PRE> <center> <h6>Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2025 <a href="http://www.he.net">Hurricane Electric</a>. All Rights Reserved.</h6></center> </body> </html>