Linux Programmer’s Manual
asprintf, vasprintf − print to allocated string
int asprintf(char **strp, const char * fmt, ...);
int vasprintf(char **strp, const char * 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, 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
When successful, these functions return the number of bytes printed, just like sprintf(3). If memory alloca-
tion wasn’t possible, or some other error occurs, these functions will return −1, and the contents of strp is
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), feature_test_macros(7)
This page is part of release 3.24 of the Linux man-pages project. A description of the project, and informa-
tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.