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NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | ATTRIBUTES | STANDARDS | HISTORY | SEE ALSO | COLOPHON |
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mkstemp(3) Library Functions Manual mkstemp(3)
mkstemp, mkostemp, mkstemps, mkostemps - create a unique
temporary file
Standard C library (libc, -lc)
#include <stdlib.h>
int mkstemp(char *template);
int mkostemp(char *template, int flags);
int mkstemps(char *template, int suffixlen);
int mkostemps(char *template, int suffixlen, int flags);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
mkstemp():
_XOPEN_SOURCE >= 500
|| /* glibc >= 2.12: */ _POSIX_C_SOURCE >= 200809L
|| /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
mkostemp():
_GNU_SOURCE
mkstemps():
/* glibc >= 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
mkostemps():
_GNU_SOURCE
The mkstemp() function generates a unique temporary filename from
template, creates and opens the file, and returns an open file
descriptor for the file.
The last six characters of template must be "XXXXXX" and these
are replaced with a string that makes the filename unique. Since
it will be modified, template must not be a string constant, but
should be declared as a character array.
The file is created with permissions 0600, that is, read plus
write for owner only. The returned file descriptor provides both
read and write access to the file. The file is opened with the
open(2) O_EXCL flag, guaranteeing that the caller is the process
that creates the file.
The mkostemp() function is like mkstemp(), with the difference
that the following bits—with the same meaning as for open(2)—may
be specified in flags: O_APPEND, O_CLOEXEC, and O_SYNC. Note
that when creating the file, mkostemp() includes the values
O_RDWR, O_CREAT, and O_EXCL in the flags argument given to
open(2); including these values in the flags argument given to
mkostemp() is unnecessary, and produces errors on some systems.
The mkstemps() function is like mkstemp(), except that the string
in template contains a suffix of suffixlen characters. Thus,
template is of the form prefixXXXXXXsuffix, and the string XXXXXX
is modified as for mkstemp().
The mkostemps() function is to mkstemps() as mkostemp() is to
mkstemp().
On success, these functions return the file descriptor of the
temporary file. On error, -1 is returned, and errno is set to
indicate the error.
EEXIST Could not create a unique temporary filename. Now the
contents of template are undefined.
EINVAL For mkstemp() and mkostemp(): The last six characters of
template were not XXXXXX; now template is unchanged.
For mkstemps() and mkostemps(): template is less than (6 +
suffixlen) characters long, or the last 6 characters
before the suffix in template were not XXXXXX.
These functions may also fail with any of the errors described
for open(2).
For an explanation of the terms used in this section, see
attributes(7).
┌─────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├─────────────────────────────────────┼───────────────┼─────────┤
│ mkstemp(), mkostemp(), mkstemps(), │ Thread safety │ MT-Safe │
│ mkostemps() │ │ │
└─────────────────────────────────────┴───────────────┴─────────┘
mkstemp()
POSIX.1-2001.
mkstemps()
BSD.
mkostemp()
mkostemps()
GNU.
mkstemp()
4.3BSD, POSIX.1-2001.
mkstemps()
glibc 2.11. BSD, Mac OS X, Solaris, Tru64.
mkostemp()
glibc 2.7.
mkostemps()
glibc 2.11.
In glibc versions 2.06 and earlier, the file is created with
permissions 0666, that is, read and write for all users. This
old behavior may be a security risk, especially since other UNIX
flavors use 0600, and somebody might overlook this detail when
porting programs. POSIX.1-2008 adds a requirement that the file
be created with mode 0600.
More generally, the POSIX specification of mkstemp() does not say
anything about file modes, so the application should make sure
its file mode creation mask (see umask(2)) is set appropriately
before calling mkstemp() (and mkostemp()).
mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.9.1.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2024-06-26. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.9.1 2024-05-02 mkstemp(3)
Pages that refer to this page: mktemp(1), getpid(2), mkdtemp(3), mktemp(3), pmprintf(3), tempnam(3), tmpfile(3), tmpnam(3), file-hierarchy(7)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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