Funny how the man page does not say that this is derived from OpenBSD. I'll include the new man page down below to show how we have improved both the program and the manual page since. It's also good for people to actually know what the flags mean. Please note that it is /usr/bin/mktemp, not /bin/mktemp like some other systems have placed our program. > Debian uses a program called `mktemp' to create temporary files in > shell scripts. Other distributions might well adopt this or a similar > solution. An excerpt from its manpage is enclosed below. > > SYNOPSIS > mktemp [-q] [-u] template > > DESCRIPTION > 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 is any file name with six > `Xs' appended to it, for example /tmp/temp.XXXXXX. The `Xs' are replaced > with the current process number and/or a unique letter combination. > Roughly 26 ** 6 combinations are tried. > > 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. > > Debian packages using mktemp in maintainer scripts must depend on de- > bianutils >= 1.7. > > 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. > > p=`basename $0` > TMPFILE=`mktemp /tmp/$p.XXXXXX` || exit 1 > echo "program output" >> $TMPFILE --------------------------------------- NAME mktemp - make temporary file name (unique) SYNOPSIS mktemp [-d] [-q] [-u] template DESCRIPTION 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 some number of `Xs' appended to it, for example /tmp/temp.XXXXXXXXXX. 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. 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. 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. -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- couraged. RETURN VALUES The mktemp utility exits with a value of 0 on success or 1 on failure. 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. TMPFILE=`mktemp /tmp/$0.XXXXXXXXXX` || exit 1 echo "program output" >> $TMPFILE In this case, we want the script to catch the error ourselves. TMPFILE=`mktemp -q /tmp/$0.XXXXXXXXXX` if [ $? -ne 0 ]; then echo "$0: Can't create temp file, exiting..." exit 1 fi Or perhaps you don't want to exit if mktemp is unable to create the file. In this case you can protect the part of the script thusly. TMPFILE=`mktemp /tmp/$0.XXXXXXXXXX` && { # Safe to use $TMPFILE in this block echo data > $TMPFILE ... rm -f $TMPFILE } SEE ALSO mkdtemp(3), mkstemp(3), mktemp(3) HISTORY The mktemp utility appeared in OpenBSD 2.1. OpenBSD 2.5 November 20, 1996 2
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