mkstemp(3)
NAME
mkstemp, mkostemp - create a unique temporary file
SYNOPSIS
#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 mkostemp(): _GNU_SOURCE mkstemps(): _BSD_SOURCE || _SVID_SOURCE mkostemps(): _GNU_SOURCE
DESCRIPTION
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().
RETURN VALUE
On success, these functions return the file descriptor of the temporary file. On error, -1 is returned, and errno is set appropriately.
ERRORS
- 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 tem
- plate 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).
VERSIONS
mkostemp() is available since glibc 2.7. mkstemps() and mkostemps()
are available since glibc 2.11.
CONFORMING TO
mkstemp(): 4.3BSD, POSIX.1-2001.
mkstemps(): unstandardized, but appears on several other systems.
mkostemp() and mkostemps(): are glibc extensions.
NOTES
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>.
SEE ALSO
mkdtemp(3), mktemp(3), tempnam(3), tmpfile(3), tmpnam(3)
COLOPHON
- This page is part of release 3.25 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/.