asprintf(3) — Linux manual page


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

NAME         top

       asprintf, vasprintf - print to allocated string

SYNOPSIS         top

       #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         top

       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         top

       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         top

       For an explanation of the terms used in this section, see

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

CONFORMING TO         top

       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         top

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

COLOPHON         top

       This page is part of release 5.13 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

GNU                            2021-03-22                    ASPRINTF(3)

Pages that refer to this page: printf(3)tracef(3)tracelog(3)