mktemp(3) Library Functions Manual mktemp(3)
NAME
mktemp - make a unique temporary filename
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <stdlib.h>
char *mktemp(char *template);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
mktemp():
Since glibc 2.12:
(_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200112L)
|| /* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
Before glibc 2.12:
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500
DESCRIPTION
Never use this function; see BUGS.
The mktemp() function generates a unique temporary filename from tem-
plate. The last six characters of template must be XXXXXX and these
are replaced with a string that makes the filename unique. Since it
will be modified, template must not be a string constant, but should be
declared as a character array.
RETURN VALUE
The mktemp() function always returns template. If a unique name was
created, the last six bytes of template will have been modified in such
a way that the resulting name is unique (i.e., does not exist already)
If a unique name could not be created, template is made an empty
string, and errno is set to indicate the error.
ERRORS
EINVAL The last six characters of template were not XXXXXX.
ATTRIBUTES
For an explanation of the terms used in this section, see at-
tributes(7).
┌────────────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────────────────────────┼───────────────┼─────────┤
│mktemp() │ Thread safety │ MT-Safe │
└────────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
4.3BSD, POSIX.1-2001. POSIX.1-2008 removes the specification of mk-
temp().
BUGS
Never use mktemp(). Some implementations follow 4.3BSD and replace
XXXXXX by the current process ID and a single letter, so that at most
26 different names can be returned. Since on the one hand the names
are easy to guess, and on the other hand there is a race between test-
ing whether the name exists and opening the file, every use of mktemp()
is a security risk. The race is avoided by mkstemp(3) and mkdtemp(3).
SEE ALSO
mktemp(1), mkdtemp(3), mkstemp(3), tempnam(3), tmpfile(3), tmpnam(3)
Linux man-pages 6.03 2023-02-05 mktemp(3)
Generated by dwww version 1.15 on Thu Aug 28 18:58:05 CEST 2025.