mktemp(3) — Linux manual page


mktemp(3)               Library Functions Manual               mktemp(3)

NAME         top

       mktemp - make a unique temporary filename

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <stdlib.h>

       char *mktemp(char *template);

   Feature Test Macro Requirements for glibc (see

           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         top

       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         top

       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         top

       EINVAL The last six characters of template were not XXXXXX.

ATTRIBUTES         top

       For an explanation of the terms used in this section, see
       │ Interface                           Attribute     Value   │
       │ mktemp()                            │ Thread safety │ MT-Safe │

STANDARDS         top


HISTORY         top

       4.3BSD, POSIX.1-2001.  Removed in POSIX.1-2008.

BUGS         top

       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).

SEE ALSO         top

       mktemp(1), mkdtemp(3), mkstemp(3), tempnam(3), tmpfile(3),

COLOPHON         top

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Linux man-pages 6.9.1          2024-05-02                      mktemp(3)

Pages that refer to this page: mktemp(1)mkdtemp(3)mkstemp(3)pmrecord(3)stdio(3)tempnam(3)tmpfile(3)tmpnam(3)