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


mktemp − make temporary file name (unique)


mktemp [−d] [−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 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.XXXXXX. 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 created with mode 0600 (unless the −u flag is given) and the filename is printed to standard output.


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.

−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.


The mktemp utility exits with a value of 0 on success, and 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


Note that one can also check to see that $TMPFILE is zero length instead of checking $?. This would allow the check to be done later one in the script (since $? would get clobbered by the next shell command).


mkstemp(3), mktemp(3)


The mktemp utility appeared in OpenBSD.

BSD November, 20, 1996 BSD