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asprintf(3) — Linux manual page

asprintf(3)              Library Functions Manualasprintf(3)

NAME        top

       asprintf, vasprintf - print to allocated string

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#define _GNU_SOURCE/* See feature_test_macros(7) */#include <stdio.h>int asprintf(char **restrictstrp, const char *restrictfmt, ...);int vasprintf(char **restrictstrp, const char *restrictfmt,va_listap);

DESCRIPTION        top

       The functionsasprintf() andvasprintf() are analogs ofsprintf(3)       andvsprintf(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 tofree(3) to release the allocated storage when       it is no longer needed.

RETURN VALUE        top

       When successful, these functions return the number of bytes       printed, just likesprintf(3).  On error, -1 is returned,errno is       set to indicate the error, and the contents ofstrp are undefined.

ERRORS        top

       Seesprintf(3) andmalloc(3).

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌───────────────────────────────┬───────────────┬────────────────┐       │Interface│Attribute│Value│       ├───────────────────────────────┼───────────────┼────────────────┤       │asprintf(),vasprintf()       │ Thread safety │ MT-Safe locale │       └───────────────────────────────┴───────────────┴────────────────┘

VERSIONS        top

       The FreeBSD implementation setsstrp to NULL on error.

STANDARDS        top

       GNU, BSD.

SEE ALSO        top

free(3),malloc(3),printf(3)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-21asprintf(3)

Pages that refer to this page:lttng_ust_tracef(3), lttng_ust_tracelog(3), printf(3), printf.h(3head)

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