MKTEMP(1)                    General Commands Manual                   MKTEMP(1)

     mktemp – make temporary file name (unique)

     mktemp [-d] [-q] [-t prefix] [-u] template ...
     mktemp [-d] [-q] [-u] -t prefix

     The mktemp utility takes each of the given file name templates and
     overwrites a portion of it to create a file name.  This file name is unique
     and suitable for use by the application.  The template may be any file name
     with some number of ‘Xs’ appended to it, for example /tmp/temp.XXXX.  The
     trailing ‘Xs’ are replaced with the current process number and/or a unique
     letter combination.  The number of unique file names mktemp can return
     depends on the number of ‘Xs’ provided; six ‘Xs’ will result in mktemp
     selecting 1 of 56800235584 (62 ** 6) possible file names.  On case-
     insensitive file systems, the effective number of unique names is
     significantly less; given six ‘Xs’, mktemp will instead select 1 of
     2176782336 (36 ** 6) possible unique file names.

     If mktemp can successfully generate a unique file name, the file is created
     with mode 0600 (unless the -u flag is given) and the filename is printed to
     standard output.

     If the -t prefix option is given, mktemp will generate a template string
     based on the prefix and the _CS_DARWIN_USER_TEMP_DIR configuration variable
     if available.  Fallback locations if _CS_DARWIN_USER_TEMP_DIR is not
     available are TMPDIR and /tmp.  Care should be taken to ensure that it is
     appropriate to use an environment variable potentially supplied by the

     If no arguments are passed or if only the -d flag is passed mktemp behaves
     as if -t tmp was supplied.

     Any number of temporary files may be created in a single invocation,
     including one based on the internal template resulting from the -t flag.

     The mktemp utility is provided to allow shell scripts to safely use
     temporary files.  Traditionally, many shell scripts take the name of the
     program with the pid as a suffix and use that as a temporary file name.
     This kind of naming scheme is predictable and the race condition it creates
     is easy for an attacker to win.  A safer, though still inferior, approach
     is to make a temporary directory using the same naming scheme.  While this
     does allow one to guarantee that a temporary file will not be subverted, it
     still allows a simple denial of service attack.  For these reasons it is
     suggested that mktemp be used instead.

     The available options are as follows:

     -d      Make a directory instead of a file.

     -q      Fail silently if an error occurs.  This is useful if a script does
             not want error output to go to standard error.

     -t prefix
             Generate a template (using the supplied prefix and TMPDIR if set)
             to create a filename template.

     -u      Operate in “unsafe” mode.  The temp file will be unlinked before
             mktemp exits.  This is slightly better than mktemp(3) but still
             introduces a race condition.  Use of this option is not encouraged.

     The mktemp utility exits 0 on success, and >0 if an error occurs.

     The following sh(1) fragment illustrates a simple use of mktemp where the
     script should quit if it cannot get a safe temporary file.

           tempfoo=`basename $0`
           TMPFILE=`mktemp /tmp/${tempfoo}.XXXXXX` || exit 1
           echo "program output" >> $TMPFILE

     To allow the use of $TMPDIR:

           tempfoo=`basename $0`
           TMPFILE=`mktemp -t ${tempfoo}` || exit 1
           echo "program output" >> $TMPFILE

     In this case, we want the script to catch the error itself.

           tempfoo=`basename $0`
           TMPFILE=`mktemp -q /tmp/${tempfoo}.XXXXXX`
           if [ $? -ne 0 ]; then
                   echo "$0: Can't create temp file, exiting..."
                   exit 1

     mkdtemp(3), mkstemp(3), mktemp(3), confstr(3), environ(7)

     A mktemp utility appeared in OpenBSD 2.1.  This implementation was written
     independently based on the OpenBSD man page, and first appeared in
     FreeBSD 2.2.7.  This man page is taken from OpenBSD.

macOS 12.1                      December 30, 2005                     macOS 12.1