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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 Any number of temporary files may be created in a single invocation,
103 including one based on the internal template resulting from the
109 utility is provided to allow shell scripts to safely use temporary files.
110 Traditionally, many shell scripts take the name of the program with
111 the pid as a suffix and use that as a temporary file name.
113 kind of naming scheme is predictable and the race condition it creates
114 is easy for an attacker to win.
115 A safer, though still inferior, approach
116 is to make a temporary directory using the same naming scheme.
118 this does allow one to guarantee that a temporary file will not be
119 subverted, it still allows a simple denial of service attack.
121 reasons it is suggested that
125 The available options are as follows:
126 .Bl -tag -width indent
128 Make a directory instead of a file.
130 Fail silently if an error occurs.
132 a script does not want error output to go to standard error.
134 Generate a template (using the supplied
138 if set) to create a filename template.
143 The temp file will be unlinked before
146 This is slightly better than
148 but still introduces a race condition.
150 option is not encouraged.
156 exits 0 on success, and 1 if an error occurs.
160 fragment illustrates a simple use of
162 where the script should quit if it cannot get a safe
164 .Bd -literal -offset indent
165 tempfoo=`basename $0`
166 TMPFILE=`mktemp /tmp/${tempfoo}.XXXXXX` || exit 1
167 echo "program output" >> $TMPFILE
170 To allow the use of $TMPDIR:
171 .Bd -literal -offset indent
172 tempfoo=`basename $0`
173 TMPFILE=`mktemp -t ${tempfoo}` || exit 1
174 echo "program output" >> $TMPFILE
177 In this case, we want the script to catch the error itself.
178 .Bd -literal -offset indent
179 tempfoo=`basename $0`
180 TMPFILE=`mktemp -q /tmp/${tempfoo}.XXXXXX`
181 if [ $? -ne 0 ]; then
182 echo "$0: Can't create temp file, exiting..."
196 This implementation was written independently based on the
201 This man page is taken from