Scroll to navigation

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


tmpnam - create a name for a temporary file


#include <stdio.h>

char *tmpnam(char *s);


The tmpnam() function returns a pointer to a string that is a valid filename, and such that a file with this name did not exist at some point in time, so that naive programmers may think it a suitable name for a temporary file. If the argument s is NULL this name is generated in an internal static buffer and may be overwritten by the next call to tmpnam(). If s is not NULL, the name is copied to the character array (of length at least L_tmpnam) pointed at by s and the value s is returned in case of success.

The path name that is created, has a directory prefix P_tmpdir. (Both L_tmpnam and P_tmpdir are defined in <stdio.h>, just like the TMP_MAX mentioned below.)


The tmpnam() function returns a pointer to a unique temporary filename, or NULL if a unique name cannot be generated.


No errors are defined.


Portable applications that use threads cannot call tmpnam() with NULL parameter if either _POSIX_THREAD_SAFE_FUNCTIONS or _POSIX_THREADS is defined.

The tmpnam() function generates a different string each time it is called, up to TMP_MAX times. If it is called more than TMP_MAX times, the behaviour is implementation defined.


Never use this function. Use mkstemp(3) instead.


SVID 2, POSIX, BSD 4.3, ISO 9899


mktemp(3), mkstemp(3), tempnam(3), tmpfile(3)

14 June 1999