MKTEMP(1)                    UNIX Reference Manual                   MKTEMP(1)

     mktemp - make temporary file name (unique)

     mktemp [-q] [-u] template

     The mktemp utility takes the given file name template and overwrites a
     portion of it to create a file name.  This file name is unique and suit-
     able for use by the application.  The template may be any file name with
     six `Xs' appended to it, for example /tmp/temp.XXXXXX. The trailing `Xs'
     are replaced with the current process number and/or a unique letter com-

     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.

     mktemp 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 sug-
     gested that mktemp be used instead.

     The available options are as follows:

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

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

     The mktemp utility exits with a value of 0 on success or 1 on failure.

     The following sh(1) fragment illustrates a simple use of mktemp where the
     script should quit if it cannot get a safe temporary file.

           TMPFILE=`mktemp /tmp/$0.XXXXXX` || exit 1
           echo "program output" >> $TMPFILE

     In this case, we want the script to catch the error itself.

           TMPFILE=`mktemp -q /tmp/$0.XXXXXX`
           if [ $? -ne 0 ]; then
                   echo "$0: Can't create temp file, exiting..."
                   exit 1

     mkstemp(3),  mktemp(3)

     The mktemp utility appeared in OpenBSD.

BSD Experimental               November 20, 1996                             1