mktemp man page on FreeBSD

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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 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 selecting 1 of 56800235584 (62 ** 6) possible file names.

     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 encour‐
	     aged.

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 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 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.

BSD			       December 30, 2005			   BSD
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