MKTEMP

Section: Linux Programmer's Manual (3)
Updated: 2008-08-06
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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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500

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).

COLOPHON

This page is part of release 3.22 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/.