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32 .\" From: $OpenBSD: mktemp.1,v 1.8 1998/03/19 06:13:37 millert Exp $
40 .Nd make temporary file name (unique)
56 utility takes each of the given file name templates and overwrites a
57 portion of it to create a file name.
58 This file name is unique
59 and suitable for use by the application.
61 any file name with some number of
68 are replaced with the current process number and/or a
69 unique letter combination.
70 The number of unique file names
72 can return depends on the number of
79 selecting 1 of 56800235584 (62 ** 6) possible file names.
83 can successfully generate a unique file name, the file
84 is created with mode 0600 (unless the
86 flag is given) and the filename is printed
93 will generate a template string based on the
97 environment variable if set.
98 The default location if
103 be taken to ensure that it is appropriate to use an environment variable
104 potentially supplied by the user.
106 If no arguments are passed or if only the
114 Any number of temporary files may be created in a single invocation,
115 including one based on the internal template resulting from the
121 utility is provided to allow shell scripts to safely use temporary files.
122 Traditionally, many shell scripts take the name of the program with
123 the pid as a suffix and use that as a temporary file name.
125 kind of naming scheme is predictable and the race condition it creates
126 is easy for an attacker to win.
127 A safer, though still inferior, approach
128 is to make a temporary directory using the same naming scheme.
130 this does allow one to guarantee that a temporary file will not be
131 subverted, it still allows a simple denial of service attack.
133 reasons it is suggested that
137 The available options are as follows:
138 .Bl -tag -width indent
140 Make a directory instead of a file.
142 Fail silently if an error occurs.
144 a script does not want error output to go to standard error.
146 Generate a template (using the supplied
150 if set) to create a filename template.
155 The temp file will be unlinked before
158 This is slightly better than
160 but still introduces a race condition.
162 option is not encouraged.
168 exits 0 on success, and 1 if an error occurs.
172 fragment illustrates a simple use of
174 where the script should quit if it cannot get a safe
176 .Bd -literal -offset indent
177 tempfoo=`basename $0`
178 TMPFILE=`mktemp /tmp/${tempfoo}.XXXXXX` || exit 1
179 echo "program output" >> $TMPFILE
182 To allow the use of $TMPDIR:
183 .Bd -literal -offset indent
184 tempfoo=`basename $0`
185 TMPFILE=`mktemp -t ${tempfoo}` || exit 1
186 echo "program output" >> $TMPFILE
189 In this case, we want the script to catch the error itself.
190 .Bd -literal -offset indent
191 tempfoo=`basename $0`
192 TMPFILE=`mktemp -q /tmp/${tempfoo}.XXXXXX`
193 if [ $? -ne 0 ]; then
194 echo "$0: Can't create temp file, exiting..."
208 This implementation was written independently based on the
213 This man page is taken from