216 lines
5.9 KiB
Groff
216 lines
5.9 KiB
Groff
.\" $NetBSD: mktemp.1,v 1.19 2009/08/15 20:44:56 wiz Exp $
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.\" From: $FreeBSD: src/usr.bin/mktemp/mktemp.1,v 1.5 1999/08/28 01:04:13 peter Exp $
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.\" From: $OpenBSD: mktemp.1,v 1.8 1998/03/19 06:13:37 millert Exp $
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.\"
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.\" Copyright (c) 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD: src/usr.bin/mktemp/mktemp.1,v 1.5 1999/08/28 01:04:13 peter Exp $
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.\"
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.Dd August 15, 2009
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.Dt MKTEMP 1
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.Os
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.Sh NAME
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.Nm mktemp
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.Nd make temporary file name (unique)
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.Sh SYNOPSIS
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.Nm mktemp
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.Op Fl dqu
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.Op Fl p Ar tmpdir
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.Bro
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.Fl t Ar prefix
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.No |
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.Ar template ...
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.Brc
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.Sh DESCRIPTION
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The
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.Nm
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utility takes each of the given file name templates and overwrites a
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portion of it to create a file name.
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This file name is unique and suitable for use by the application.
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The template may be any file name with some number of
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.Ql X Ns s
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appended to it, for example
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.Pa /tmp/temp.XXXX .
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The trailing
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.Ql X Ns s
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are replaced with the current process number and/or a
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unique letter combination.
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The number of unique file names
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.Nm
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can return depends on the number of
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.Ql X Ns s
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provided; six
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.Ql X Ns s
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will result in
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.Nm
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testing roughly 26 ** 6 combinations.
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.Pp
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If
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.Nm
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can successfully generate a unique file name, the file
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is created with mode 0600 (unless the
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.Fl u
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flag is given) and the filename is printed to standard output.
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.Pp
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If the
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.Fl t Ar prefix
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option is given,
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.Nm
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will generate a template string based on the
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.Ar prefix
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and the
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.Ev TMPDIR
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environment variable, if set.
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The default location if
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.Ev TMPDIR
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is not set is
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.Pa /tmp .
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The default location of the temporary directory can be overridden with the
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.Fl p Ar tmpdir
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option.
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The template string created will consist of the
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.Ar prefix
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followed by a
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.So . Sc
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and an eight character unique letter combination.
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.Ql X Ns s
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in the
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.Ar prefix
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string will be treated as literal.
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If an additional
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.Ar template
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argument is passed, a second file will be created.
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Care should be taken to ensure that it is appropriate to use an
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environment variable potentially supplied by the user.
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.Pp
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Any number of temporary files may be created in a single invocation
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using multiple
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.Ar template
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arguments, also a single one based on the internal template with the
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.Fl t
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option value as filename prefix.
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.Pp
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At least one
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.Ar template
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argument or the
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.Fl t
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option must be present.
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.Pp
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.Nm
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is provided to allow shell scripts to safely use temporary files.
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Traditionally, many shell scripts take the name of the program with
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the pid as a suffix and use that as a temporary file name.
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This kind of naming scheme is predictable and the race condition
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it creates is easy for an attacker to win.
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A safer, though still inferior, approach
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is to make a temporary directory using the same naming scheme.
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While this does allow one to guarantee that a temporary file will
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not be subverted, it still allows a simple denial of service attack.
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For these reasons it is suggested that
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.Nm
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be used instead.
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.Sh OPTIONS
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The available options are as follows:
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.Bl -tag -width indent
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.It Fl d
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Make a directory instead of a file.
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.It Fl q
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Fail silently if an error occurs.
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This is useful if
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a script does not want error output to go to standard error.
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.It Fl t Ar prefix
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Generate a template (using the supplied
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.Ar prefix
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and
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.Ev TMPDIR
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if set) to create a filename template.
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If
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.Fl t Ar prefix
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and
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.Ar template
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are both given,
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.Ar prefix
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will not apply to
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.Ar template .
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.It Fl u
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Operate in
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.Dq unsafe
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mode.
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The temp file will be unlinked before
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.Nm
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exits.
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This is slightly better than
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.Xr mktemp 3
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but still introduces a race condition.
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Use of this option is not encouraged.
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.El
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.Sh EXIT STATUS
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The
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.Nm
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utility exits with a value of 0 on success, and 1 on any failure.
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.Sh EXAMPLES
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The following
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.Xr sh 1
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fragment illustrates a simple use of
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.Nm
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where the script should quit if it cannot get a safe
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temporary file.
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.Bd -literal -offset indent
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TMPFILE=`mktemp /tmp/${0##*/}.XXXXXX` || exit 1
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echo "program output" \*[Gt]\*[Gt] $TMPFILE
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.Ed
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.Pp
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To allow the use of $TMPDIR:
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.Bd -literal -offset indent
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TMPFILE=`mktemp -t ${0##*/}` || exit 1
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echo "program output" \*[Gt]\*[Gt] $TMPFILE
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.Ed
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.Pp
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In this case, we want the script to catch the error itself.
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.Bd -literal -offset indent
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TMPFILE=`mktemp -q /tmp/${0##*/}.XXXXXX`
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if [ $? -ne 0 ]; then
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echo "$0: Can't create temp file, exiting..."
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exit 1
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fi
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.Ed
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.Sh SEE ALSO
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.Xr mkdtemp 3 ,
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.Xr mkstemp 3 ,
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.Xr mktemp 3 ,
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.Xr environ 7
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.Sh HISTORY
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The
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.Nm
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utility appeared in
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.Nx 1.5 .
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It has been imported from
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.Fx ,
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the idea and the manual page were taken from
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.Ox .
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