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28 .\" From: $OpenBSD: mktemp.1,v 1.8 1998/03/19 06:13:37 millert Exp $
36 .Nd make temporary file name (unique)
52 utility takes each of the given file name templates and overwrites a
53 portion of it to create a file name.
54 This file name is unique
55 and suitable for use by the application.
57 any file name with some number of
64 are replaced with the current process number and/or a
65 unique letter combination.
66 The number of unique file names
68 can return depends on the number of
75 selecting 1 of 56800235584 (62 ** 6) possible file names.
79 can successfully generate a unique file name, the file
80 is created with mode 0600 (unless the
82 flag is given) and the filename is printed
89 will generate a template string based on the
93 environment variable if set.
94 The default location if
99 be taken to ensure that it is appropriate to use an environment variable
100 potentially supplied by the user.
102 If no arguments are passed or if only the
110 Any number of temporary files may be created in a single invocation,
111 including one based on the internal template resulting from the
117 utility is provided to allow shell scripts to safely use temporary files.
118 Traditionally, many shell scripts take the name of the program with
119 the pid as a suffix and use that as a temporary file name.
121 kind of naming scheme is predictable and the race condition it creates
122 is easy for an attacker to win.
123 A safer, though still inferior, approach
124 is to make a temporary directory using the same naming scheme.
126 this does allow one to guarantee that a temporary file will not be
127 subverted, it still allows a simple denial of service attack.
129 reasons it is suggested that
133 The available options are as follows:
134 .Bl -tag -width indent
136 Make a directory instead of a file.
138 Fail silently if an error occurs.
140 a script does not want error output to go to standard error.
142 Generate a template (using the supplied
146 if set) to create a filename template.
151 The temp file will be unlinked before
154 This is slightly better than
156 but still introduces a race condition.
158 option is not encouraged.
165 fragment illustrates a simple use of
167 where the script should quit if it cannot get a safe
169 .Bd -literal -offset indent
170 tempfoo=`basename $0`
171 TMPFILE=`mktemp /tmp/${tempfoo}.XXXXXX` || exit 1
172 echo "program output" >> $TMPFILE
175 To allow the use of $TMPDIR:
176 .Bd -literal -offset indent
177 tempfoo=`basename $0`
178 TMPFILE=`mktemp -t ${tempfoo}` || exit 1
179 echo "program output" >> $TMPFILE
182 In this case, we want the script to catch the error itself.
183 .Bd -literal -offset indent
184 tempfoo=`basename $0`
185 TMPFILE=`mktemp -q /tmp/${tempfoo}.XXXXXX`
186 if [ $? -ne 0 ]; then
187 echo "$0: Can't create temp file, exiting..."
201 This implementation was written independently based on the
206 This man page is taken from