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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 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 mktemp can
     return depends on the number of `Xs' provided; six `Xs' will result in
     mktemp testing roughly 26 ** 6 combinations.

     If mktemp can successfully generate a unique file name, the file is cre-
     ated 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 tem-
     porary 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 cre-
     ates 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.

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 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.

	   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 writ-
     ten independently based on the OpenBSD man page, and first appeared in
     FreeBSD 2.2.7.  This man page is taken from OpenBSD

FreeBSD 5.4		       November 20, 1996		   FreeBSD 5.4

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