371 lines
7.3 KiB
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371 lines
7.3 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of MKSTEMP</TITLE>
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</HEAD><BODY>
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<H1>MKSTEMP</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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mkstemp, mkostemp, mkstemps, mkostemps - create a unique temporary file
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/stdlib.h">stdlib.h</A>></B>
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<B>int mkstemp(char *</B><I>template</I><B>);</B>
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<B>int mkostemp(char *</B><I>template</I><B>, int </B><I>flags</I><B>);</B>
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<B>int mkstemps(char *</B><I>template</I><B>, int </B><I>suffixlen</I><B>);</B>
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<B>int mkostemps(char *</B><I>template</I><B>, int </B><I>suffixlen</I><B>, int </B><I>flags</I><B>);</B>
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</PRE>
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>mkstemp</B>():
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<DL COMPACT><DT id="1"><DD>
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_XOPEN_SOURCE >= 500
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<BR> || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
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<BR> || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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</DL>
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<P>
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<B>mkostemp</B>():
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_GNU_SOURCE
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<BR>
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<B>mkstemps</B>():
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<BR> /* Glibc since 2.19: */ _DEFAULT_SOURCE
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<BR> || /* Glibc versions <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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<BR>
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<B>mkostemps</B>():
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_GNU_SOURCE
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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The
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<B>mkstemp</B>()
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function generates a unique temporary filename from
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<I>template</I>,
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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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<P>
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The last six characters of
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<I>template</I>
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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</I>
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must not be a string constant, but should be declared as a character array.
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<P>
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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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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2)
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<B>O_EXCL</B>
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flag, guaranteeing that the caller is the process that creates the file.
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<P>
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The
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<B>mkostemp</B>()
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function is like
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<B>mkstemp</B>(),
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with the difference that the following bits---with the same meaning as for
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2)---may
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be specified in
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<I>flags</I>:
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<B>O_APPEND</B>,
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<B>O_CLOEXEC</B>,
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and
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<B>O_SYNC</B>.
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Note that when creating the file,
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<B>mkostemp</B>()
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includes the values
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<B>O_RDWR</B>,
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<B>O_CREAT</B>,
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and
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<B>O_EXCL</B>
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in the
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<I>flags</I>
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argument given to
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2);
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including these values in the
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<I>flags</I>
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argument given to
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<B>mkostemp</B>()
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is unnecessary, and produces errors on some
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systems.
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<P>
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The
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<B>mkstemps</B>()
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function is like
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<B>mkstemp</B>(),
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except that the string in
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<I>template</I>
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contains a suffix of
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<I>suffixlen</I>
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characters.
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Thus,
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<I>template</I>
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is of the form
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<I>prefixXXXXXXsuffix</I>,
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and the string XXXXXX is modified as for
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<B>mkstemp</B>().
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<P>
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The
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<B>mkostemps</B>()
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function is to
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<B>mkstemps</B>()
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as
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<B>mkostemp</B>()
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is to
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<B>mkstemp</B>().
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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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</I>
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is set appropriately.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="2"><B>EEXIST</B>
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<DD>
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Could not create a unique temporary filename.
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Now the contents of <I>template</I> are undefined.
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<DT id="3"><B>EINVAL</B>
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<DD>
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For
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<B>mkstemp</B>()
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and
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<B>mkostemp</B>():
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The last six characters of <I>template</I> were not XXXXXX;
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now <I>template</I> is unchanged.
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<DT id="4"><DD>
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For
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<B>mkstemps</B>()
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and
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<B>mkostemps</B>():
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<I>template</I>
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is less than
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<I>(6 + suffixlen)</I>
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characters long, or the last 6 characters before the suffix in
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<I>template</I>
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were not XXXXXX.
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</DL>
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<P>
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These functions may also fail with any of the errors described for
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<B><A HREF="/cgi-bin/man/man2html?2+open">open</A></B>(2).
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<A NAME="lbAG"> </A>
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<H2>VERSIONS</H2>
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<B>mkostemp</B>()
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is available since glibc 2.7.
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<B>mkstemps</B>()
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and
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<B>mkostemps</B>()
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are available since glibc 2.11.
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<A NAME="lbAH"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>mkstemp</B>(),
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<B>mkostemp</B>(),
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<BR>
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<B>mkstemps</B>(),
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<B>mkostemps</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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<B>mkstemp</B>():
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4.3BSD, POSIX.1-2001.
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<P>
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<B>mkstemps</B>():
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unstandardized, but appears on several other systems.
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<P>
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<B>mkostemp</B>()
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and
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<B>mkostemps</B>():
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are glibc extensions.
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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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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<P>
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More generally, the POSIX specification of
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<B>mkstemp</B>()
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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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<B><A HREF="/cgi-bin/man/man2html?2+umask">umask</A></B>(2))
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is set appropriately before calling
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<B>mkstemp</B>()
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(and
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<B>mkostemp</B>()).
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<A NAME="lbAK"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+mkdtemp">mkdtemp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+mktemp">mktemp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+tempnam">tempnam</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+tmpfile">tmpfile</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+tmpnam">tmpnam</A></B>(3)
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<A NAME="lbAL"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="5"><A HREF="#lbAB">NAME</A><DD>
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<DT id="6"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="7"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="8"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="9"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="10"><A HREF="#lbAG">VERSIONS</A><DD>
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<DT id="11"><A HREF="#lbAH">ATTRIBUTES</A><DD>
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<DT id="12"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="13"><A HREF="#lbAJ">NOTES</A><DD>
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<DT id="14"><A HREF="#lbAK">SEE ALSO</A><DD>
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<DT id="15"><A HREF="#lbAL">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:48 GMT, March 31, 2021
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