Section (3) mkstemp
mkstemp, mkostemp, mkstemps, mkostemps — create a unique temporary file
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.
mkostemp() function is
mkstemp(), with the
difference that the following bits—with the same
meaning as for open(2)(emmay be specified
O_SYNC. Note that when creating the file,
mkostemp() includes the values
O_EXCL in the
flags argument given to
open(2); including these
values in the
argument given to
unnecessary, and produces errors on some systems.
mkstemps() function is
mkstemp(), except that the
contains a suffix of
suffixlen characters. Thus,
template is of the
the string XXXXXX is modified as for
mkostemps() function is
mkostemp() is to
On success, these functions return the file descriptor of
the temporary file. On error, −1 is returned, and
errno is set appropriately.
Could not create a unique temporary filename. Now the contents of
mkostemp(): The last six characters of
templatewere not XXXXXX; now
templateis less than (6 + suffixlen) characters long, or the last 6 characters before the suffix in
templatewere not XXXXXX.
These functions may also fail with any of the errors described for open(2).
mkostemp() is available
since glibc 2.7.
mkostemps() are available since
For an explanation of the terms used in this section, see attributes(7).
but appears on several other systems.
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
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Copyright 1993 David Metcalfe (davidprism.demon.co.uk)
and Copyright (C) 2008, Michael Kerrisk <mtk.manpagesgmail.com>
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Linux libc source code
Lewine_zsingle_quotesz_s _POSIX Programmer_zsingle_quotesz_s Guide_ (O_zsingle_quotesz_Reilly & Associates, 1991)
386BSD man pages
Modified Sat Jul 24 18:48:48 1993 by Rik Faith (faithcs.unc.edu)
Modified 980310, aeb
Modified 990328, aeb
2008-06-19, mtk, Added mkostemp(); various other changes