Linux manual pages Section 3: Subroutines  

Name

mktemp — make a unique temporary filename

Synopsis

#include <stdlib.h>
char *mktemp( char *template);
 
[Note] Note
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, and errno is set to indicate the error.

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 3.52 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/.


  Copyright (C) 1993 David Metcalfe (davidprism.demon.co.uk)

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References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified Sat Jul 24 18:48:06 1993 by Rik Faith (faithcs.unc.edu)
Modified Fri Jun 23 01:26:34 1995 by Andries Brouwer (aebcwi.nl)
(prompted by Scott Burkett <scottbIntNet.net>)
Modified Sun Mar 28 23:44:38 1999 by Andries Brouwer (aebcwi.nl)