537 lines
12 KiB
HTML
537 lines
12 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 GETUTENT</TITLE>
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</HEAD><BODY>
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<H1>GETUTENT</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2019-08-02<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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getutent, getutid, getutline, pututline, setutent, endutent,
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utmpname - access utmp file entries
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/utmp.h">utmp.h</A>></B>
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<P>
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<B>struct utmp *getutent(void);</B>
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<BR>
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<B>struct utmp *getutid(const struct utmp *</B><I>ut</I><B>);</B>
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<BR>
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<B>struct utmp *getutline(const struct utmp *</B><I>ut</I><B>);</B>
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<P>
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<B>struct utmp *pututline(const struct utmp *</B><I>ut</I><B>);</B>
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<P>
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<B>void setutent(void);</B>
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<BR>
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<B>void endutent(void);</B>
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<P>
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<B>int utmpname(const char *</B><I>file</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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New applications should use the POSIX.1-specified "utmpx" versions of
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these functions; see CONFORMING TO.
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<P>
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<B>utmpname</B>()
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sets the name of the utmp-format file for the other utmp
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functions to access.
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If
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<B>utmpname</B>()
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is not used to set the filename
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before the other functions are used, they assume <B>_PATH_UTMP</B>, as
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defined in <I><<A HREF="file:///usr/include/paths.h">paths.h</A>></I>.
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<P>
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<B>setutent</B>()
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rewinds the file pointer to the beginning of the utmp file.
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It is generally a good idea to call it before any of the other
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functions.
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<P>
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<B>endutent</B>()
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closes the utmp file.
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It should be called when the user
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code is done accessing the file with the other functions.
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<P>
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<B>getutent</B>()
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reads a line from the current file position in the utmp file.
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It returns a pointer to a structure containing the fields of
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the line.
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The definition of this structure is shown in
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<B><A HREF="/cgi-bin/man/man2html?5+utmp">utmp</A></B>(5).
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<P>
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<B>getutid</B>()
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searches forward from the current file position in the utmp
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file based upon <I>ut</I>.
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If <I>ut->ut_type</I> is one of <B>RUN_LVL</B>,
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<B>BOOT_TIME</B>, <B>NEW_TIME</B>, or <B>OLD_TIME</B>,
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<B>getutid</B>()
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will
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find the first entry whose <I>ut_type</I> field matches <I>ut->ut_type</I>.
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If <I>ut->ut_type</I> is one of <B>INIT_PROCESS</B>, <B>LOGIN_PROCESS</B>,
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<B>USER_PROCESS</B>, or <B>DEAD_PROCESS</B>,
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<B>getutid</B>()
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will find the
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first entry whose
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<I>ut_id</I>
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field matches <I>ut->ut_id</I>.
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<P>
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<B>getutline</B>()
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searches forward from the current file position in the utmp file.
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It scans entries whose
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<I>ut_type</I>
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is <B>USER_PROCESS</B>
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or <B>LOGIN_PROCESS</B> and returns the first one whose
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<I>ut_line</I>
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field
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matches <I>ut->ut_line</I>.
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<P>
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<B>pututline</B>()
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writes the
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<I>utmp</I>
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structure <I>ut</I> into the utmp file.
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It uses
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<B>getutid</B>()
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to search for the proper place in the file to insert
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the new entry.
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If it cannot find an appropriate slot for <I>ut</I>,
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<B>pututline</B>()
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will append the new entry to the end of the file.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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<B>getutent</B>(),
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<B>getutid</B>(),
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and
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<B>getutline</B>()
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return a pointer to a <I>struct utmp</I> on success,
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and NULL on failure (which includes the "record not found" case).
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This <I>struct utmp</I> is allocated in static storage, and may be
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overwritten by subsequent calls.
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<P>
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On success
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<B>pututline</B>()
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returns
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<I>ut</I>;
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on failure, it returns NULL.
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<P>
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<B>utmpname</B>()
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returns 0 if the new name was successfully stored, or -1 on failure.
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<P>
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In the event of an error, these functions
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<I>errno</I>
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set to indicate the cause.
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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="1"><B>ENOMEM</B>
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<DD>
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Out of memory.
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<DT id="2"><B>ESRCH</B>
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<DD>
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Record not found.
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</DL>
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<P>
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<B>setutent</B>(),
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<B>pututline</B>(),
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and the
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<B>getut*</B>()
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functions can also fail for the reasons described in
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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>FILES</H2>
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<DL COMPACT>
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<DT id="3"><I>/var/run/utmp</I>
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<DD>
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database of currently logged-in users
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<DT id="4"><I>/var/log/wtmp</I>
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<DD>
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database of past user logins
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</DL>
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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>getutent</B>()
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</TD><TD>Thread safety</TD><TD>
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MT-Unsafe init race:utent
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<BR>
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race:utentbuf sig:ALRM timer
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<BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>getutid</B>(),
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<BR>
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<B>getutline</B>()
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</TD><TD>Thread safety</TD><TD>
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MT-Unsafe init race:utent
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<BR>
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sig:ALRM timer
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<BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>pututline</B>()
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</TD><TD>Thread safety</TD><TD>
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MT-Unsafe race:utent
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<BR>
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sig:ALRM timer
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<BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>setutent</B>(),
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<BR>
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<B>endutent</B>(),
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<BR>
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<B>utmpname</B>()
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</TD><TD>Thread safety</TD><TD>MT-Unsafe race:utent<BR></TD></TR>
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</TABLE>
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<P>
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In the above table,
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<I>utent</I>
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in
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<I>race:utent</I>
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signifies that if any of the functions
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<B>setutent</B>(),
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<B>getutent</B>(),
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<B>getutid</B>(),
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<B>getutline</B>(),
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<B>pututline</B>(),
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<B>utmpname</B>(),
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or
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<B>endutent</B>()
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are used in parallel in different threads of a program,
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then data races could occur.
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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XPG2, SVr4.
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<P>
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In XPG2 and SVID 2 the function
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<B>pututline</B>()
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is documented to return void, and that is what it does on many systems
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(AIX, HP-UX).
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HP-UX introduces a new function
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<B>_pututline</B>()
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with the prototype given above for
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<B>pututline</B>().
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<P>
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All these functions are obsolete now on non-Linux systems.
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POSIX.1-2001 and POSIX.1-2008, following SUSv1,
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does not have any of these functions, but instead uses
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<P>
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<B>#include <<A HREF="file:///usr/include/utmpx.h">utmpx.h</A>></B>
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<P>
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<B>struct utmpx *getutxent(void);</B>
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<B>struct utmpx *getutxid(const struct utmpx *);</B>
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<B>struct utmpx *getutxline(const struct utmpx *);</B>
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<B>struct utmpx *pututxline(const struct utmpx *);</B>
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<B>void setutxent(void);</B>
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<B>void endutxent(void);</B>
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<P>
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These functions are provided by glibc,
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and perform the same task as their equivalents without the "x", but use
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<I>struct utmpx</I>,
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defined on Linux to be the same as
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<I>struct utmp</I>.
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For completeness, glibc also provides
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<B>utmpxname</B>(),
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although this function is not specified by POSIX.1.
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<P>
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On some other systems,
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the <I>utmpx</I> structure is a superset of the <I>utmp</I> structure,
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with additional fields, and larger versions of the existing fields,
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and parallel files are maintained, often
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<I>/var/*/utmpx</I>
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and
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<I>/var/*/wtmpx</I>.
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<P>
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Linux glibc on the other hand does not use a parallel <I>utmpx</I> file
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since its <I>utmp</I> structure is already large enough.
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The "x" functions listed above are just aliases for
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their counterparts without the "x" (e.g.,
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<B>getutxent</B>()
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is an alias for
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<B>getutent</B>()).
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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<A NAME="lbAK"> </A>
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<H3>Glibc notes</H3>
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The above functions are not thread-safe.
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Glibc adds reentrant versions
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<P>
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<B>#include <<A HREF="file:///usr/include/utmp.h">utmp.h</A>></B>
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<P>
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<B>int getutent_r(struct utmp *</B><I>ubuf</I><B>, struct utmp **</B><I>ubufp</I><B>);</B>
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<P>
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<B>int getutid_r(struct utmp *</B><I>ut</I><B>,</B>
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<B> struct utmp *</B><I>ubuf</I><B>, struct utmp **</B><I>ubufp</I><B>);</B>
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<P>
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<B>int getutline_r(struct utmp *</B><I>ut</I><B>,</B>
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<B> struct utmp *</B><I>ubuf</I><B>, struct utmp **</B><I>ubufp</I><B>);</B>
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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>getutent_r</B>(),
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<B>getutid_r</B>(),
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<B>getutline_r</B>():
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<PRE>
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_GNU_SOURCE
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|| /* since glibc 2.19: */ _DEFAULT_SOURCE
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|| /* glibc <= 2.19: */ _SVID_SOURCE || _BSD_SOURCE
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</PRE>
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<P>
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These functions are GNU extensions, analogs of the functions of the
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same name without the _r suffix.
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The
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<I>ubuf</I>
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argument gives these functions a place to store their result.
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On success, they return 0, and a pointer to the result is written in
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<I>*ubufp</I>.
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On error, these functions return -1.
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There are no utmpx equivalents of the above functions.
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(POSIX.1 does not specify such functions.)
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<A NAME="lbAL"> </A>
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<H2>EXAMPLE</H2>
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The following example adds and removes a utmp record, assuming it is run
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from within a pseudo terminal.
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For usage in a real application, you
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should check the return values of
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<B><A HREF="/cgi-bin/man/man2html?3+getpwuid">getpwuid</A></B>(3)
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and
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<B><A HREF="/cgi-bin/man/man2html?3+ttyname">ttyname</A></B>(3).
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<P>
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#include <<A HREF="file:///usr/include/string.h">string.h</A>>
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#include <<A HREF="file:///usr/include/stdlib.h">stdlib.h</A>>
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#include <<A HREF="file:///usr/include/pwd.h">pwd.h</A>>
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#include <<A HREF="file:///usr/include/unistd.h">unistd.h</A>>
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#include <<A HREF="file:///usr/include/utmp.h">utmp.h</A>>
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#include <<A HREF="file:///usr/include/time.h">time.h</A>>
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<P>
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int
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main(int argc, char *argv[])
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{
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<BR> struct utmp entry;
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<P>
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<BR> system("echo before adding entry:;who");
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<P>
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<BR> entry.ut_type = USER_PROCESS;
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<BR> entry.ut_pid = getpid();
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<BR> strcpy(entry.ut_line, ttyname(STDIN_FILENO) + strlen("/dev/"));
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<BR> /* only correct for ptys named /dev/tty[pqr][0-9a-z] */
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<BR> strcpy(entry.ut_id, ttyname(STDIN_FILENO) + strlen("/dev/tty"));
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<BR> time(&entry.ut_time);
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<BR> strcpy(entry.ut_user, getpwuid(getuid())->pw_name);
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<BR> memset(entry.ut_host, 0, UT_HOSTSIZE);
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<BR> entry.ut_addr = 0;
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<BR> setutent();
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<BR> pututline(&entry);
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<P>
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<BR> system("echo after adding entry:;who");
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<P>
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<BR> entry.ut_type = DEAD_PROCESS;
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<BR> memset(entry.ut_line, 0, UT_LINESIZE);
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<BR> entry.ut_time = 0;
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<BR> memset(entry.ut_user, 0, UT_NAMESIZE);
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<BR> setutent();
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<BR> pututline(&entry);
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<P>
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<BR> system("echo after removing entry:;who");
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<P>
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<BR> endutent();
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<BR> exit(EXIT_SUCCESS);
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}
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<A NAME="lbAM"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+getutmp">getutmp</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?5+utmp">utmp</A></B>(5)
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<A NAME="lbAN"> </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">FILES</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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<DL>
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<DT id="14"><A HREF="#lbAK">Glibc notes</A><DD>
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</DL>
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<DT id="15"><A HREF="#lbAL">EXAMPLE</A><DD>
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<DT id="16"><A HREF="#lbAM">SEE ALSO</A><DD>
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<DT id="17"><A HREF="#lbAN">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: 00:05:44 GMT, March 31, 2021
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