asprintf, vasprintf - print to allocated string
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.
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.
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