NAME

mktemp — create temporary file or directory

SYNOPSIS

DESCRIPTION

Creates a file u=rw - umask (directory u=rwx - umask if -d), replacing a run of ‘X’ characters in the template, and writes its path to the standard output stream. If no template, defaults to "tmp.XXXXXXXXXX" and -t. The final path is "[directory[/]]template[suffix]".

The template must contain at least three consecutive ‘X’es after its final slash (if any). These are replaced with random alphanumeric characters until a path that doesn't already exist is generated; this behaviour, coupled with the mode, makes mktemp suitable for safely generating unique temporary files (unless -u).

At most $\min \left(\right(\mathrm{alphabet-length}=62{)}^{\mathrm{x-count}},2^{64}-1)$ filenames will be tried. This limit is unlikely to be hit, or hittable, with any more than three ‘X’es.

OPTIONS

-d, --directory

Create a directory instead of a regular file.

-q, --quiet

Suppress error output. The EXIT STATUS is unaffected.

-u, --dry-run

Don't create anything, just output a matching path that doesn't exist. Do not use this — there's no guarantee the file can be created in the first place, and the file may be used or subverted by a third party before the mktemp output is used.

-t, --tmpdir

If the TMPDIR environment variable is set, equivalent to -p TMPDIR, otherwise to -p /tmp.

-p, --tmpdir=directory

Prepend directory[/] to the template.

-s, --suffix=suffix

Append suffix to the template after parsing it: no amount of ‘X’es will interfere with the template pattern.

ENVIRONMENT

TMPDIR

Used if -p, -t, or no template.

EXIT STATUS

1 if -u and faccessat(2) failed for a reason other than ENOENT, otherwise if open(2)/mkdir(2) failed for a reason other than EEXIST. In case of a write error, created files are removed.

EXAMPLES

$ mktemp
/tmp/tmp.K2EHQCo6LG
$ mktemp -p .cache
.cache/tmp.Vp2q7gVUX5

$ mktemp inXXX.jpeg
inpBH.jpeg
$ TMPDIR=~/.cache mktemp -t inXXX.jpeg
/home/cicada/.cache/inq8e.jpeg

Or, as part of a script:

#!/bin/sh
tmpfile="$(mktemp)" || exit
echo "Program output." > "$tmpfile"

#!/bin/sh
exec > "$(mktemp /var/tmp/cleanup-XXXXXXXX.log)" || exit

SEE ALSO

mkdir(2), open(2), mkstemp(3)

STANDARDS

Compatible with the GNU system; short -s and allowing -s when template doesn't end with an ‘X’ are extensions.

OpenBSD supports -dqutp with TMPDIR overriding -p, its template must end with the ‘X’es, and the minimum amount thereof is 6. NetBSD allows any amount of ‘X’es, -p overrides TMPDIR, supports any amount of templates, and its -t prefix injects a "prefix.XXXXXXXX" template. FreeBSD is as NetBSD but drops -p. All three of those implementations first create the file with -u, then remove it. An OpenBSD-compatible mktemp also exists in the illumos gate.

The only strictly-IEEE Std 1003.1-2008 (“POSIX.1”)-compliant way to emulate mktemp is to use

HISTORY

Originates from OpenBSD 2.1 as mktemp(1):

A compatible implementation appeared in FreeBSD 3.0, adding -t prefix, which constructs a template in the form "${TMPDIR:-/tmp}[/]prefix.XXXXXXXX" and allows any amount of templates afterward, with a default mktemp prefix. This was imported into NetBSD 1.5.

OpenBSD 3.0 adds -tp, as present-day.

NetBSD 6.1 adds -p tmpdir, with the highest priority.