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

NAME
     mmkktteemmpp - make temporary file name (unique)

SYNOPSIS
     mmkktteemmpp [-dd] [-qq] [-tt prefix] [-uu] template ...
     mmkktteemmpp [-dd] [-qq] [-uu] -tt prefix

DESCRIPTION
     The mmkktteemmpp utility takes each of the given file name templates and over-
     writes 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 mmkktteemmpp can
     return depends on the number of `Xs' provided; six `Xs' will result in
     mmkktteemmpp testing roughly 26 ** 6 combinations.

     If mmkktteemmpp can successfully generate a unique file name, the file is cre-
     ated with mode 0600 (unless the -uu flag is given) and the filename is
     printed to standard output.

     If the -tt prefix option is given, mmkktteemmpp will generate an 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 -tt flag.

     MMkktteemmpp 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 nam-
     ing 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 mmkktteemmpp be used instead.

OOPPTTIIOONNSS
     The available options are as follows:

     -dd      Make a directory instead of a file.

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

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

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

DIAGNOSTICS     The mmkktteemmpp utility exits 0 on success, and 1 if an error occurs.

EEXXAAMMPPLLEESS
     The following sh(1) fragment illustrates a simple use of mmkktteemmpp 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
           fi

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

HISTORY
     A mmkktteemmpp utility appeared in OpenBSD 2.1.  This implementation was writ-
     ten independently based on the OpenBSD man page, and first appeared in
     FreeBSD 2.2.7.  This man page is taken from OpenBSD

BSD                            November 20, 1996                           BSD