303 lines
11 KiB
HTML
303 lines
11 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 -->
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>write</title>
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<basefont size="3"> <a name="write"></a> <a name="tag_04_172"></a><!-- write -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_04_172_01"></a>NAME</h4>
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<blockquote>write - write to another user</blockquote>
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<h4><a name="tag_04_172_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('UP')">UP</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> write</tt> <i>user_name</i> <b>[</b><i>terminal</i><b>]</b><tt><img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></tt></code></div>
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</blockquote>
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<h4><a name="tag_04_172_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>write</i> utility shall read lines from the user's standard input and write them to the terminal of another user. When
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first invoked, it shall write the message:</p>
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<pre>
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<b>Message from</b> <i>sender-login-id</i> <tt>(</tt><i>sending-terminal</i><tt>)</tt> <b>[</b><i>date</i><b>]</b><tt>...
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</tt>
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</pre>
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<p>to <i>user_name</i>. When it has successfully completed the connection, the sender's terminal shall be alerted twice to indicate
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that what the sender is typing is being written to the recipient's terminal.</p>
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<p>If the recipient wants to reply, this can be accomplished by typing:</p>
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<pre>
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<tt>write</tt> <i>sender-login-id</i> <b>[</b><i>sending-terminal</i><b>]</b>
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</pre>
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<p>upon receipt of the initial message. Whenever a line of input as delimited by an NL, EOF, or EOL special character (see the Base
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Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap11.html#tag_11">Chapter 11, General Terminal
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Interface</a>) is accumulated while in canonical input mode, the accumulated data shall be written on the other user's terminal.
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Characters shall be processed as follows:</p>
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<ul>
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<li>
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<p>Typing <alert> shall write the alert character to the recipient's terminal.</p>
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</li>
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<li>
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<p>Typing the erase and kill characters shall affect the sender's terminal in the manner described by the <b>termios</b> interface
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in the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap11.html#tag_11">Chapter 11, General
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Terminal Interface</a>.</p>
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</li>
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<li>
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<p>Typing the interrupt or end-of-file characters shall cause <i>write</i> to write an appropriate message ( <tt>"EOT\n"</tt> in
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the POSIX locale) to the recipient's terminal and exit.</p>
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</li>
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<li>
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<p>Typing characters from <i>LC_CTYPE</i> classifications <b>print</b> or <b>space</b> shall cause those characters to be sent to
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the recipient's terminal.</p>
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</li>
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<li>
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<p>When and only when the <a href="../utilities/stty.html"><i>stty</i></a> <b>iexten</b> local mode is enabled, the existence and
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processing of additional special control characters and multi-byte or single-byte functions is implementation-defined.</p>
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</li>
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<li>
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<p>Typing other non-printable characters shall cause implementation-defined sequences of printable characters to be written to the
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recipient's terminal.</p>
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</li>
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</ul>
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<p>To write to a user who is logged in more than once, the <i>terminal</i> argument can be used to indicate which terminal to write
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to; otherwise, the recipient's terminal is selected in an implementation-defined manner and an informational message is written to
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the sender's standard output, indicating which terminal was chosen.</p>
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<p>Permission to be a recipient of a <i>write</i> message can be denied or granted by use of the <a href=
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"../utilities/mesg.html"><i>mesg</i></a> utility. However, a user's privilege may further constrain the domain of accessibility of
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other users' terminals. The <i>write</i> utility shall fail when the user lacks the appropriate privileges to perform the requested
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action.</p>
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</blockquote>
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<h4><a name="tag_04_172_04"></a>OPTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_172_05"></a>OPERANDS</h4>
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<blockquote>
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<p>The following operands shall be supported:</p>
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<dl compact>
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<dt><i>user_name</i></dt>
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<dd>Login name of the person to whom the message shall be written. The application shall ensure that this operand is of the form
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returned by the <a href="../utilities/who.html"><i>who</i></a> utility.</dd>
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<dt><i>terminal</i></dt>
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<dd>Terminal identification in the same format provided by the <a href="../utilities/who.html"><i>who</i></a> utility.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_172_06"></a>STDIN</h4>
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<blockquote>
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<p>Lines to be copied to the recipient's terminal are read from standard input.</p>
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</blockquote>
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<h4><a name="tag_04_172_07"></a>INPUT FILES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_172_08"></a>ENVIRONMENT VARIABLES</h4>
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<blockquote>
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<p>The following environment variables shall affect the execution of <i>write</i>:</p>
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<dl compact>
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<dt><i>LANG</i></dt>
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<dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> for
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the precedence of internationalization variables used to determine the values of locale categories.)</dd>
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<dt><i>LC_ALL</i></dt>
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<dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
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<dt><i>LC_CTYPE</i></dt>
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<dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments and input files). If the recipient's locale does not use an <i>LC_CTYPE</i>
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equivalent to the sender's, the results are undefined.</dd>
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<dt><i>LC_MESSAGES</i></dt>
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<dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and
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informative messages written to standard output.</dd>
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<dt><i>NLSPATH</i></dt>
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<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt=
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"[Option End]" border="0"></dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_172_09"></a>ASYNCHRONOUS EVENTS</h4>
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<blockquote>
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<p>If an interrupt signal is received, <i>write</i> shall write an appropriate message on the recipient's terminal and exit with a
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status of zero. It shall take the standard action for all other signals.</p>
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</blockquote>
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<h4><a name="tag_04_172_10"></a>STDOUT</h4>
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<blockquote>
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<p>An informational message shall be written to standard output if a recipient is logged in more than once.</p>
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</blockquote>
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<h4><a name="tag_04_172_11"></a>STDERR</h4>
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<blockquote>
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<p>The standard error shall be used only for diagnostic messages.</p>
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</blockquote>
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<h4><a name="tag_04_172_12"></a>OUTPUT FILES</h4>
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<blockquote>
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<p>The recipient's terminal is used for output.</p>
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</blockquote>
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<h4><a name="tag_04_172_13"></a>EXTENDED DESCRIPTION</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_172_14"></a>EXIT STATUS</h4>
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<blockquote>
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<p>The following exit values shall be returned:</p>
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<dl compact>
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<dt> 0</dt>
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<dd>Successful completion.</dd>
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<dt>>0</dt>
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<dd>The addressed user is not logged on or the addressed user denies permission.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_172_15"></a>CONSEQUENCES OF ERRORS</h4>
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<blockquote>
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<p>Default.</p>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_04_172_16"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>The <a href="../utilities/talk.html"><i>talk</i></a> utility is considered by some users to be a more usable utility on
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full-screen terminals.</p>
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</blockquote>
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<h4><a name="tag_04_172_17"></a>EXAMPLES</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_172_18"></a>RATIONALE</h4>
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<blockquote>
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<p>The <i>write</i> utility was included in this volume of IEEE Std 1003.1-2001 since it can be implemented on all
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terminal types. The standard developers considered the <a href="../utilities/talk.html"><i>talk</i></a> utility, which cannot be
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implemented on certain terminals, to be a "better" communications interface. Both of these programs are in widespread use on
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historical implementations. Therefore, the standard developers decided that both utilities should be specified.</p>
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<p>The format of the terminal name is unspecified, but the descriptions of <a href="../utilities/ps.html"><i>ps</i></a>, <a href=
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"../utilities/talk.html"><i>talk</i></a>, <a href="../utilities/who.html"><i>who</i></a>, and <i>write</i> require that they all
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use or accept the same format.</p>
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</blockquote>
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<h4><a name="tag_04_172_19"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_04_172_20"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="mesg.html"><i>mesg</i></a> , <a href="talk.html"><i>talk</i></a> , <a href="who.html"><i>who</i></a> , the Base
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Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap11.html#tag_11">Chapter 11, General Terminal
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Interface</a></p>
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</blockquote>
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<h4><a name="tag_04_172_21"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 2.</p>
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</blockquote>
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<h4><a name="tag_04_172_22"></a>Issue 5</h4>
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<blockquote>
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<p>The FUTURE DIRECTIONS section is added.</p>
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</blockquote>
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<h4><a name="tag_04_172_23"></a>Issue 6</h4>
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<blockquote>
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<p>This utility is marked as part of the User Portability Utilities option.</p>
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<p>The normative text is reworded to avoid use of the term "must" for application requirements.</p>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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<hr size="2" noshade>
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<center><font size="2"><!--footer start-->
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
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"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
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