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32 .\" @(#)mktemp.3 8.1 (Berkeley) 6/4/93
40 .Nd make temporary file name (unique)
44 .Fd #include <unistd.h>
46 .Fn mktemp "char *template"
48 .Fn mkstemp "char *template"
50 .Fn mkstemps "char *template" "int suffixlen"
52 .Fn mkdtemp "char *template"
57 takes the given file name template and overwrites a portion of it
58 to create a file name.
59 This file name is unique and suitable for use
61 The template may be 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 testing roughly 26 ** 6 combinations.
84 makes the same replacement to the template and creates the template file,
85 mode 0600, returning a file descriptor opened for reading and writing.
86 This avoids the race between testing for a file's existence and opening it
91 function acts the same as
93 except it permits a suffix to exist in the template.
94 The template should be of the form
95 .Pa /tmp/tmpXXXXXXsuffix .
97 is told the length of the suffix string.
101 function makes the same replacement to the template as in
103 and creates the template directory, mode 0700.
109 functions return a pointer to the template on success and
117 return \-1 if no suitable file could be created.
118 If either call fails an error code is placed in the global variable
129 to one of the following values:
132 The pathname portion of the template is not an existing directory.
143 to any value specified by the
154 to any value specified by the
163 to any value specified by the
167 A common problem that results in a core dump is that the programmer
168 passes in a read-only string to
174 This is common with programs that were developed before
176 compilers were common.
180 .Qq /tmp/tempfile.XXXXXX
181 will result in a core dump due to
183 attempting to modify the string constant that was given.
184 If the program in question makes heavy use of that type
185 of function call, you do have the option of compiling the program
186 so that it will store string constants in a writable segment of memory.
189 for more information.
191 This family of functions produces filenames which can be guessed.
192 This makes the race in
194 between testing for a file's existence and opening it for use,
195 particularly dangerous from a security perspective.
196 Whenever it is possible,
198 should be used instead.
212 function first appeared in
218 function first appeared in