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MKTEMP(1)               FreeBSD 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

     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 TMPDIR environment variable if set.  The
     default location if TMPDIR is not set is /tmp.  Care should be taken to
     ensure that it is appropriate to use an environment variable potentially
     supplied by the user.

     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

     The mktemp utility exits 0 on success, and 1 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), 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.

FreeBSD 11.0-PRERELEASE        December 30, 2005       FreeBSD 11.0-PRERELEASE


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