MKTEMP(3)

NAME
mktemp - make a unique temporary filename

SYNOPSIS
#include <stdlib.h>

char *mktemp(char *template);

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

mktemp():
    Since glibc 2.12:
        _BSD_SOURCE || _SVID_SOURCE ||
            (_XOPEN_SOURCE >= 500 ||
                 _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
            !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
    Before glibc 2.12:
        _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

DESCRIPTION
The mktemp() function generates a unique temporary filename from template. 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.

ERRORS

EINVAL
    The last six characters of template were not XXXXXX.

CONFORMING TO
4.3BSD, POSIX.1-2001. POSIX.1-2008 removes the specification of mktemp().

NOTES
The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows the Single UNIX Specification and has the prototype in <stdlib.h>.

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 testing whether the name exists and opening the file, every use of mktemp() is a security risk. The race is avoided by mkstemp(3).

SEE ALSO
mkstemp(3), tempnam(3), tmpfile(3), tmpnam(3)

COLOPHON
This page is part of release 3.29 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.