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MKTEMP(1) DragonFly 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.
If no arguments are passed or if only the -d flag is passed mktemp
behaves as if -t tmp was supplied.
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.
EXIT STATUS
The mktemp utility exits 0 on success, and >0 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.
DragonFly 3.5 November 3, 2012 DragonFly 3.5