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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | ATTRIBUTES | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
MKSTEMP(3) Linux Programmer's Manual MKSTEMP(3)
mkstemp, mkostemp, mkstemps, mkostemps - create a unique temporary
file
#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
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
|| /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
mkostemp(): _GNU_SOURCE
mkstemps():
/* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 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
appropriately.
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).
mkostemp() is available since glibc 2.7. mkstemps() and mkostemps()
are available since glibc 2.11.
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├────────────────────────┼───────────────┼─────────┤
│mkstemp(), mkostemp(), │ Thread safety │ MT-Safe │
│mkstemps(), mkostemps() │ │ │
└────────────────────────┴───────────────┴─────────┘
mkstemp(): 4.3BSD, POSIX.1-2001.
mkstemps(): unstandardized, but appears on several other systems.
mkostemp() and mkostemps(): are glibc extensions.
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 release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2016-10-08 MKSTEMP(3)
Pages that refer to this page: getpid(2), mkdtemp(3), mktemp(3), pmprintf(3), tempnam(3), tmpfile(3), tmpnam(3), file-hierarchy(7)