| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON | The Linux Programming Interface |
MKSTEMP(3) Linux Programmer's Manual MKSTEMP(3)
mkstemp, mkostemp - 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():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200112L
mkostemp(): _GNU_SOURCE
mkstemps(): _BSD_SOURCE || _SVID_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. (In glibc versions 2.06 and earlier, the file is created with
permissions 0666, that is, read and write for all users.) 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 flags as
for open(2) may be specified in flags (e.g., O_APPEND, O_SYNC).
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.
mkstemp(): 4.3BSD, POSIX.1-2001.
mkstemps(): unstandardized, but appears on several other systems.
mkostemp() and mkostemps(): are glibc extensions.
The old behavior of creating a file with mode 0666 may be a security risk,
especially since other UNIX flavors use 0600, and somebody might overlook this
detail when porting programs.
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()).
The prototype for mktemp() is in <unistd.h> for libc4, libc5, glibc1; glibc2
follows POSIX.1 and has the prototype in <stdlib.h>.
mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-09-26 MKSTEMP(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface