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28 .\" @(#)mktemp.3 8.1 (Berkeley) 6/4/93
36 .Nd make temporary file name (unique)
42 .Fn mktemp "char *template"
44 .Fn mkstemp "char *template"
46 .Fn mkostemp "char *template" "int oflags"
48 .Fn mkostemps "char *template" "int suffixlen" "int oflags"
50 .Fn mkdtemp "char *template"
53 .Fn mkstemps "char *template" "int suffixlen"
58 takes the given file name template and overwrites a portion of it
59 to create a file name.
60 This file name is guaranteed not to exist at the time of function invocation
61 and is suitable for use
63 The template may be any file name with some number of
67 .Pa /tmp/temp.XXXXXX .
71 unique alphanumeric combination.
72 The number of unique file names
74 can return depends on the number of
81 selecting one of 56800235584 (62 ** 6) possible temporary file names.
86 makes the same replacement to the template and creates the template file,
87 mode 0600, returning a file descriptor opened for reading and writing.
88 This avoids the race between testing for a file's existence and opening it
96 but allows specifying additional
100 The permitted flags are
113 functions act the same as
118 except they permit a suffix to exist in the template.
119 The template should be of the form
120 .Pa /tmp/tmpXXXXXXsuffix .
126 are told the length of the suffix string.
130 function makes the same replacement to the template as in
132 and creates the template directory, mode 0700.
138 functions return a pointer to the template on success and
148 return \-1 if no suitable file could be created.
149 If either call fails an error code is placed in the global variable
162 to one of the following values:
165 The pathname portion of the template is not an existing directory.
175 to the following value:
193 to any value specified by the
206 to any value specified by the
215 to any value specified by the
219 A common problem that results in a core dump is that the programmer
220 passes in a read-only string to
226 This is common with programs that were developed before
228 compilers were common.
232 .Qq /tmp/tempfile.XXXXXX
233 will result in a core dump due to
235 attempting to modify the string constant that was given.
242 function prototypes are also available from
255 functions are expected to conform to
259 function is expected to conform to
261 and is not specified by
268 functions do not conform to any standard.
280 function first appeared in
286 function first appeared in
294 functions appeared in
297 This family of functions produces filenames which can be guessed,
298 though the risk is minimized when large numbers of
301 increase the number of possible temporary filenames.
302 This makes the race in
304 between testing for a file's existence (in the
307 and opening it for use
308 (later in the user application)
309 particularly dangerous from a security perspective.
310 Whenever it is possible,
314 should be used instead, since it does not have the race condition.
317 cannot be used, the filename created by
319 should be created using the
323 and the return status of the call should be tested for failure.
324 This will ensure that the program does not continue blindly
325 in the event that an attacker has already created the file
326 with the intention of manipulating or reading its contents.