1MKSTEMP(3) Linux Programmer's Manual MKSTEMP(3)
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6 mkstemp, mkostemp - create a unique temporary file
7
9 #include <stdlib.h>
10 int mkstemp(char *template);
12 int mkostemp (char *template, int flags);
14 int mkstemps(char *template, int suffixlen);
16 int mkostemps(char *template, int suffixlen, int flags);
18 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
20 mkstemp(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500
22 mkostemp(): _GNU_SOURCE
23 mkstemps(): _BSD_SOURCE || _SVID_SOURCE
24 mkostemps(): _GNU_SOURCE
25
27 The mkstemp() function generates a unique temporary filename from tem‐
28 plate, creates and opens the file, and returns an open file descriptor
29 for the file.
30 The last six characters of template must be "XXXXXX" and these are
32 replaced with a string that makes the filename unique. Since it will
33 be modified, template must not be a string constant, but should be
34 declared as a character array.
35 The file is created with permissions 0600, that is, read plus write for
37 owner only. (In glibc versions 2.06 and earlier, the file is created
38 with permissions 0666, that is, read and write for all users.) The
39 returned file descriptor provides both read and write access to the
40 file. The file is opened with the open(2) O_EXCL flag, guaranteeing
41 that the caller is the process that creates the file.
42 The mkostemp() function is like mkstemp(), with the difference that
44 flags as for open(2) may be specified in flags (e.g., O_APPEND,
45 O_SYNC).
46 The mkstemps() function is like mkstemp(), except that the string in
48 template contains a suffix of suffixlen characters. Thus, template is
49 of the form prefixXXXXXXsuffix, and the string XXXXXX is modified as
50 for mkstemp().
51 The mkostemps() function is to mkstemps() as mkostemp() is to
53 mkstemp().
54
56 On success, these functions return the file descriptor of the temporary
57 file. On error, -1 is returned, and errno is set appropriately.
58
60 EEXIST Could not create a unique temporary filename. Now the contents
61 of template are undefined.
62 EINVAL For mkstemp() and mkostemp(): The last six characters of tem‐
64 plate were not XXXXXX; now template is unchanged.
65 For mkstemps() and mkostemps() template is less than (6 + suf‐
67 fixlen) characters long, or the last 6 characters before the
68 suffix in template were not XXXXXX.
69 These functions may also fail with any of the errors described for
71 open(2).
72
74 mkostemp() is available since glibc 2.7. mkstemps() and mkostemps()
75 are available since glibc 2.11.
76
78 mkstemp(): 4.3BSD, POSIX.1-2001.
79 mkstemps(): unstandardized, but appears on several other systems.
81 mkostemp() and mkostemps(): are glibc extensions.
83
85 The old behavior of creating a file with mode 0666 may be a security
86 risk, especially since other Unix flavors use 0600, and somebody might
87 overlook this detail when porting programs.
88 More generally, the POSIX specification of mkstemp() does not say any‐
90 thing about file modes, so the application should make sure its file
91 mode creation mask (see umask(2)) is set appropriately before calling
92 mkstemp() (and mkostemp()).
93 The prototype for mktemp() is in <unistd.h> for libc4, libc5, glibc1;
95 glibc2 follows POSIX.1 and has the prototype in <stdlib.h>.
96
98 mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)
99
101 This page is part of release 3.25 of the Linux man-pages project. A
102 description of the project, and information about reporting bugs, can
103 be found at http://www.kernel.org/doc/man-pages/.
104GNU 2010-06-19 MKSTEMP(3)