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MKTEMP(1)                 BSD General Commands Manual                MKTEMP(1)

NAME
     mktemp -- make temporary file name (unique)

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

DESCRIPTION
     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.

     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 inter-nal internal
     nal 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 sub-verted, subverted,
     verted, it still allows a simple denial of service attack.  For these reasons it is suggested that
     mktemp be used instead.

OPTIONS
     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 tem-plate. template.
             plate.

     -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.

EXIT STATUS
     The mktemp utility exits 0 on success, and 1 if an error occurs.

EXAMPLES
     The following sh(1) fragment illustrates a simple use of mktemp where the script should quit if it can-not cannot
     not 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
           fi

SEE ALSO
     mkdtemp(3), mkstemp(3), mktemp(3), environ(7)

HISTORY
     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.

BSD                            December 30, 2005                           BSD

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