mktemp (3) - Linux Manuals

mktemp: make a unique temporary filename

Command to display mktemp manual in Linux: $ man 3 mktemp

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:: (_XOPEN_SOURCE >= 500) && ! (_POSIX_C_SOURCE >= 200112L)
|| /* Glibc since 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 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.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
mktemp()	Thread safety	MT-Safe

CONFORMING TO

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

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) and mkdtemp(3).

COLOPHON

This page is part of release 5.10 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.