Manpages - asprintf.3

asprintf, vasprintf - print to allocated string

  #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);

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.

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.

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

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.

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

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