mirror of https://github.com/mkerrisk/man-pages
256 lines
6.2 KiB
Groff
256 lines
6.2 KiB
Groff
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
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.\" and Copyright (C) 2008, Michael Kerrisk <mtk.manpages@gmail.com>
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.\" References consulted:
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.\" Linux libc source code
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.\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
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.\" 386BSD man pages
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.\" Modified Sat Jul 24 18:48:48 1993 by Rik Faith (faith@cs.unc.edu)
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.\" Modified 980310, aeb
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.\" Modified 990328, aeb
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.\" 2008-06-19, mtk, Added mkostemp(); various other changes
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.\"
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.TH MKSTEMP 3 2016-10-08 "GNU" "Linux Programmer's Manual"
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.SH NAME
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mkstemp, mkostemp, mkstemps, mkostemps \- create a unique temporary file
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.SH SYNOPSIS
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.nf
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.B #include <stdlib.h>
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.sp
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.BI "int mkstemp(char *" template );
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.sp
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.BI "int mkostemp(char *" template ", int " flags );
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.sp
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.BI "int mkstemps(char *" template ", int " suffixlen );
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.sp
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.BI "int mkostemps(char *" template ", int " suffixlen ", int " flags );
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.fi
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR mkstemp ():
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.ad l
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.RS 4
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.PD 0
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_XOPEN_SOURCE\ >=\ 500
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.\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
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|| /* Since glibc 2.12: */ _POSIX_C_SOURCE\ >=\ 200809L
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|| /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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.PD
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.RE
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.ad b
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.PP
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.BR mkostemp ():
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_GNU_SOURCE
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.br
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.BR mkstemps ():
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/* Glibc since 2.19: */ _DEFAULT_SOURCE
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|| /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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.br
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.BR mkostemps ():
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_GNU_SOURCE
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.SH DESCRIPTION
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The
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.BR mkstemp ()
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function generates a unique temporary filename from
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.IR template ,
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creates and opens the file,
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and returns an open file descriptor for the file.
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The last six characters of
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.I template
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must be "XXXXXX" and these are replaced with a string that makes the
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filename unique.
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Since it will be modified,
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.I template
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must not be a string constant, but should be declared as a character array.
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The file is created with
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permissions 0600, that is, read plus write for owner only.
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The returned file descriptor provides both read and write access to the file.
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The file is opened with the
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.BR open (2)
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.B O_EXCL
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flag, guaranteeing that the caller is the process that creates the file.
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The
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.BR mkostemp ()
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function is like
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.BR mkstemp (),
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with the difference that the following bits\(emwith the same meaning as for
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.BR open (2)\(emmay
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be specified in
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.IR flags :
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.BR O_APPEND ,
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.BR O_CLOEXEC ,
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and
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.BR O_SYNC .
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Note that when creating the file,
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.BR mkostemp ()
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includes the values
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.BR O_RDWR ,
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.BR O_CREAT ,
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and
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.BR O_EXCL
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in the
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.I flags
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argument given to
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.BR open (2);
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including these values in the
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.I flags
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argument given to
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.BR mkostemp ()
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is unnecessary, and produces errors on some
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.\" Reportedly, FreeBSD
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systems.
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The
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.BR mkstemps ()
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function is like
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.BR mkstemp (),
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except that the string in
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.I template
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contains a suffix of
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.I suffixlen
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characters.
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Thus,
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.I template
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is of the form
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.IR "prefixXXXXXXsuffix" ,
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and the string XXXXXX is modified as for
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.BR mkstemp ().
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The
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.BR mkostemps ()
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function is to
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.BR mkstemps ()
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as
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.BR mkostemp ()
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is to
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.BR mkstemp ().
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.SH RETURN VALUE
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On success, these functions return the file descriptor
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of the temporary file.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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.TP
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.B EEXIST
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Could not create a unique temporary filename.
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Now the contents of \fItemplate\fP are undefined.
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.TP
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.B EINVAL
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For
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.BR mkstemp ()
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and
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.BR mkostemp ():
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The last six characters of \fItemplate\fP were not XXXXXX;
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now \fItemplate\fP is unchanged.
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.sp
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For
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.BR mkstemps ()
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and
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.BR mkostemps ():
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.I template
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is less than
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.I "(6 + suffixlen)"
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characters long, or the last 6 characters before the suffix in
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.I template
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were not XXXXXX.
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.PP
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These functions may also fail with any of the errors described for
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.BR open (2).
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.SH VERSIONS
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.BR mkostemp ()
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is available since glibc 2.7.
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.BR mkstemps ()
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and
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.BR mkostemps ()
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are available since glibc 2.11.
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.SH ATTRIBUTES
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For an explanation of the terms used in this section, see
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.BR attributes (7).
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.TS
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allbox;
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lbw23 lb lb
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l l l.
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Interface Attribute Value
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T{
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.BR mkstemp (),
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.BR mkostemp (),
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.br
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.BR mkstemps (),
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.BR mkostemps ()
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T} Thread safety MT-Safe
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.TE
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.SH CONFORMING TO
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.BR mkstemp ():
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4.3BSD, POSIX.1-2001.
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.BR mkstemps ():
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unstandardized, but appears on several other systems.
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.\" mkstemps() appears to be at least on the BSDs, Mac OS X, Solaris,
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.\" and Tru64.
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.BR mkostemp ()
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and
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.BR mkostemps ():
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are glibc extensions.
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.SH NOTES
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In glibc versions 2.06 and earlier, the file is created with permissions 0666,
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that is, read and write for all users.
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This old behavior may be
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a security risk, especially since other UNIX flavors use 0600,
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and somebody might overlook this detail when porting programs.
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POSIX.1-2008 adds a requirement that the file be created with mode 0600.
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More generally, the POSIX specification of
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.BR mkstemp ()
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does not say anything
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about file modes, so the application should make sure its
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file mode creation mask (see
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.BR umask (2))
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is set appropriately before calling
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.BR mkstemp ()
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(and
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.BR mkostemp ()).
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.\"
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.\" The prototype for
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.\" .BR mkstemp ()
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.\" is in
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.\" .I <unistd.h>
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.\" for libc4, libc5, glibc1; glibc2 follows POSIX.1 and has the prototype in
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.\" .IR <stdlib.h> .
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.SH SEE ALSO
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.BR mkdtemp (3),
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.BR mktemp (3),
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.BR tempnam (3),
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.BR tmpfile (3),
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.BR tmpnam (3)
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