Annotation of src/usr.bin/mktemp/mktemp.1, Revision 1.13
1.13 ! millert 1: .\" $OpenBSD: mktemp.1,v 1.12 1999/08/05 09:19:35 millert Exp $
1.1 millert 2: .\"
1.13 ! millert 3: .\" Copyright (c) 1996, 2000 Todd C. Miller <Todd.Miller@courtesan.com>
! 4: .\" All rights reserved.
1.1 millert 5: .\"
6: .\" Redistribution and use in source and binary forms, with or without
7: .\" modification, are permitted provided that the following conditions
8: .\" are met:
9: .\" 1. Redistributions of source code must retain the above copyright
10: .\" notice, this list of conditions and the following disclaimer.
11: .\" 2. Redistributions in binary form must reproduce the above copyright
12: .\" notice, this list of conditions and the following disclaimer in the
13: .\" documentation and/or other materials provided with the distribution.
1.13 ! millert 14: .\" 3. The name of the author may not be used to endorse or promote products
! 15: .\" derived from this software without specific prior written permission.
1.1 millert 16: .\"
1.13 ! millert 17: .\" THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
! 18: .\" INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
! 19: .\" AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
! 20: .\" THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
! 21: .\" EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
! 22: .\" PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
! 23: .\" OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
! 24: .\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
! 25: .\" OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
! 26: .\" ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 millert 27: .\"
1.11 aaron 28: .Dd November 20, 1996
1.1 millert 29: .Dt MKTEMP 1
30: .Os
31: .Sh NAME
32: .Nm mktemp
33: .Nd make temporary file name (unique)
34: .Sh SYNOPSIS
35: .Nm mktemp
1.5 millert 36: .Op Fl d
37: .Op Fl q
1.1 millert 38: .Op Fl u
39: .Ar template
40: .Sh DESCRIPTION
41: The
42: .Nm mktemp
43: utility takes the given file name template and overwrites a
1.13 ! millert 44: portion of it to create a unique file name. The template may be
1.1 millert 45: any file name with some number of
46: .Ql X Ns s
47: appended
48: to it, for example
1.12 millert 49: .Pa /tmp/temp.XXXXXXXXXX .
1.1 millert 50: The trailing
51: .Ql X Ns s
1.13 ! millert 52: are replaced with a combination of the the current process number and
! 53: random letters. The name chosen depends both on the number of
! 54: .Ql X Ns s
! 55: in the template and the number of collisions with pre-existing files.
1.1 millert 56: The number of unique file names
57: .Nm
58: can return depends on the number of
59: .Ql X Ns s
1.13 ! millert 60: provided; ten
1.1 millert 61: .Ql X Ns s
62: will
63: result in
64: .Nm
1.13 ! millert 65: testing roughly 26 ** 10 combinations.
1.1 millert 66: .Pp
67: If
68: .Nm
1.13 ! millert 69: can successfully generate a unique file name, the file (or directory)
! 70: is created with file permissions such that it is only readable and writable
! 71: by its owner (unless the
1.1 millert 72: .Fl u
1.13 ! millert 73: flag is given) and the filename is printed to standard output.
1.8 millert 74: .Pp
1.10 aaron 75: .Nm mktemp
1.8 millert 76: is provided to allow shell scripts to safely use temporary files.
77: Traditionally, many shell scripts take the name of the program with
1.10 aaron 78: the PID as a suffix and use that as a temporary file name. This
1.8 millert 79: kind of naming scheme is predictable and the race condition it creates
1.10 aaron 80: is easy for an attacker to win. A safer, though still inferior approach
1.8 millert 81: is to make a temporary directory using the same naming scheme. While
82: this does allow one to guarantee that a temporary file will not be
83: subverted, it still allows a simple denial of service attack. For these
84: reasons it is suggested that
85: .Nm
86: be used instead.
1.1 millert 87: .Sh OPTIONS
88: .Bl -tag -width indent
89: The available options are as follows:
1.5 millert 90: .It Fl d
91: Make a directory instead of a file.
92: .It Fl q
93: Fail silently if an error occurs. This is useful if
94: a script does not want error output to go to standard error.
1.1 millert 95: .It Fl u
96: Operate in
97: .Dq unsafe
98: mode. The temp file will be unlinked before
99: .Nm
100: exits. This is slightly better than
101: .Fn mktemp 3
102: but still introduces a race condition. Use of this
103: option is not encouraged.
1.6 millert 104: .El
1.1 millert 105: .Sh RETURN VALUES
106: The
107: .Nm
108: utility
1.10 aaron 109: exits with a value of 0 on success or 1 on failure.
1.1 millert 110: .Sh EXAMPLES
111: The following
112: .Xr sh 1
113: fragment illustrates a simple use of
114: .Nm
115: where the script should quit if it cannot get a safe
116: temporary file.
117: .Bd -literal -offset indent
1.12 millert 118: TMPFILE=`mktemp /tmp/$0.XXXXXXXXXX` || exit 1
1.1 millert 119: echo "program output" >> $TMPFILE
120: .Ed
121: .Pp
1.12 millert 122: In this case, we want the script to catch the error ourselves.
1.1 millert 123: .Bd -literal -offset indent
1.12 millert 124: TMPFILE=`mktemp -q /tmp/$0.XXXXXXXXXX`
1.2 millert 125: if [ $? -ne 0 ]; then
1.1 millert 126: echo "$0: Can't create temp file, exiting..."
127: exit 1
128: fi
1.12 millert 129: .Ed
130: .Pp
131: Or perhaps you don't want to exit if
132: .Nm
133: is unable to create the file. In this case you can protect the
134: part of the script thusly.
135: .Bd -literal -offset indent
136: TMPFILE=`mktemp /tmp/$0.XXXXXXXXXX` && {
137: # Safe to use $TMPFILE in this block
138: echo data > $TMPFILE
139: ...
140: rm -f $TMPFILE
141: }
1.1 millert 142: .Ed
143: .Sh SEE ALSO
1.8 millert 144: .Xr mkdtemp 3 ,
1.10 aaron 145: .Xr mkstemp 3 ,
146: .Xr mktemp 3
1.1 millert 147: .Sh HISTORY
148: The
149: .Nm
150: utility appeared in
1.7 millert 151: .Ox 2.1 .
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