344 lines
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344 lines
13 KiB
HTML
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<title>talk</title>
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<basefont size="3"> <a name="talk"></a> <a name="tag_04_138"></a><!-- talk -->
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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_138_01"></a>NAME</h4>
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<blockquote>talk - talk to another user</blockquote>
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<h4><a name="tag_04_138_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"> talk</tt> <i>address</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_138_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>talk</i> utility is a two-way, screen-oriented communication program.</p>
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<p>When first invoked, <i>talk</i> shall send a message similar to:</p>
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<pre>
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<tt>Message from <</tt><i>unspecified string</i><tt>>
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talk: connection requested by</tt> <i>your_address</i><tt>talk: respond with: talk</tt> <i>your_address</i>
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</pre>
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<p>to the specified <i>address</i>. At this point, the recipient of the message can reply by typing:</p>
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<pre>
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<tt>talk</tt> <i>your_address</i>
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</pre>
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<p>Once communication is established, the two parties can type simultaneously, with their output displayed in separate regions of
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the screen. Characters shall be processed as follows:</p>
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<ul>
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<li>
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<p>Typing the alert character shall alert the recipient's terminal.</p>
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</li>
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<li>
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<p>Typing <control>-L shall cause the sender's screen regions to be refreshed.</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 terminate the local <i>talk</i> utility. Once the <i>talk</i> session has
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been terminated on one side, the other side of the <i>talk</i> session shall be notified that the <i>talk</i> session has been
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terminated and shall be able to do nothing except 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 shall be 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 sent 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>Permission to be a recipient of a <i>talk</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>talk</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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<p>Certain block-mode terminals do not have all the capabilities necessary to support the simultaneous exchange of messages
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required for <i>talk</i>. When this type of exchange cannot be supported on such terminals, the implementation may support an
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exchange with reduced levels of simultaneous interaction or it may report an error describing the terminal-related deficiency.</p>
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</blockquote>
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<h4><a name="tag_04_138_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_138_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>address</i></dt>
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<dd>The recipient of the <i>talk</i> session. One form of <i>address</i> is the <<i>user name</i>>, as returned by the
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<a href="../utilities/who.html"><i>who</i></a> utility. Other address formats and how they are handled are unspecified.</dd>
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<dt><i>terminal</i></dt>
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<dd>If the recipient is logged in more than once, the <i>terminal</i> argument can be used to indicate the appropriate terminal
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name. If <i>terminal</i> is not specified, the <i>talk</i> message shall be displayed on one or more accessible terminals in use by
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the recipient. The format of <i>terminal</i> shall be the same as that returned by the <a href=
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"../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_138_06"></a>STDIN</h4>
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<blockquote>
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<p>Characters read from standard input shall be copied to the recipient's terminal in an unspecified manner. If standard input is
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not a terminal, talk shall write a diagnostic message and exit with a non-zero status.</p>
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</blockquote>
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<h4><a name="tag_04_138_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_138_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>talk</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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<dt><i>TERM</i></dt>
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<dd>Determine the name of the invoker's terminal type. If this variable is unset or null, an unspecified default terminal type
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shall be used.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_138_09"></a>ASYNCHRONOUS EVENTS</h4>
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<blockquote>
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<p>When the <i>talk</i> utility receives a SIGINT signal, the utility shall terminate and exit with a zero status. It shall take
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the standard action for all other signals.</p>
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</blockquote>
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<h4><a name="tag_04_138_10"></a>STDOUT</h4>
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<blockquote>
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<p>If standard output is a terminal, characters copied from the recipient's standard input may be written to standard output.
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Standard output also may be used for diagnostic messages. If standard output is not a terminal, <i>talk</i> shall exit with a
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non-zero status.</p>
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</blockquote>
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<h4><a name="tag_04_138_11"></a>STDERR</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_138_12"></a>OUTPUT 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_138_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_138_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>An error occurred or <i>talk</i> was invoked on a terminal incapable of supporting it.</dd>
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</dl>
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</blockquote>
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<h4><a name="tag_04_138_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_138_16"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Because the handling of non-printable, non- <space>s is tied to the <a href="../utilities/stty.html"><i>stty</i></a>
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description of <b>iexten</b>, implementation extensions within the terminal driver can be accessed. For example, some
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implementations provide line editing functions with certain control character sequences.</p>
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</blockquote>
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<h4><a name="tag_04_138_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_138_18"></a>RATIONALE</h4>
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<blockquote>
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<p>The <a href="../utilities/write.html"><i>write</i></a> utility was included in this volume of IEEE Std 1003.1-2001
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since it can be implemented on all terminal types. The <i>talk</i> utility, which cannot be implemented on certain terminals, was
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considered to be a "better" communications interface. Both of these programs are in widespread use on historical implementations.
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Therefore, both utilities have been specified.</p>
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<p>All references to networking abilities (<i>talk</i>ing to a user on another system) were removed as being outside the scope of
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this volume of IEEE Std 1003.1-2001.</p>
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<p>Historical BSD and System V versions of <i>talk</i> terminate both of the conversations when either user breaks out of the
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session. This can lead to adverse consequences if a user unwittingly continues to enter text that is interpreted by the shell when
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the other terminates the session. Therefore, the version of <i>talk</i> specified by this volume of IEEE Std 1003.1-2001
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requires both users to terminate their end of the session explicitly.</p>
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<p>Only messages sent to the terminal of the invoking user can be internationalized in any way:</p>
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<ul>
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<li>
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<p>The original "Message from <<i>unspecified string</i>> ..." message sent to the terminal of the recipient cannot be
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internationalized because the environment of the recipient is as yet inaccessible to the <i>talk</i> utility. The environment of
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the invoking party is irrelevant.</p>
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</li>
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<li>
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<p>Subsequent communication between the two parties cannot be internationalized because the two parties may specify different
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languages in their environment (and non-portable characters cannot be mapped from one language to another).</p>
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</li>
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<li>
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<p>Neither party can be required to communicate in a language other than C and/or the one specified by their environment because
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unavailable terminal hardware support (for example, fonts) may be required.</p>
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</li>
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</ul>
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<p>The text in the STDOUT section reflects the usage of the verb "display" in this section; some <i>talk</i> implementations
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actually use standard output to write to the terminal, but this volume of IEEE Std 1003.1-2001 does not require that to
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be the case.</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>,
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<i>talk</i>, <a href="../utilities/who.html"><i>who</i></a>, and <a href="../utilities/write.html"><i>write</i></a> require that
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they all use or accept the same format.</p>
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<p>The handling of non-printable characters is partially implementation-defined because the details of mapping them to printable
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sequences is not needed by the user. Historical implementations, for security reasons, disallow the transmission of non-printable
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characters that may send commands to the other terminal.</p>
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</blockquote>
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<h4><a name="tag_04_138_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_138_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="stty.html"><i>stty</i></a> , <a href="who.html"><i>who</i></a> , <a href=
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"write.html"><i>write</i></a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/xbd_chap11.html#tag_11">Chapter 11, General Terminal Interface</a></p>
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</blockquote>
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<h4><a name="tag_04_138_21"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 4.</p>
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</blockquote>
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<h4><a name="tag_04_138_22"></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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</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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