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22 <script language="JavaScript" src="../jscript/codes.js"></script><basefont size="3">
23 <center><font size="2">The Open Group Base Specifications Issue 8<br>
24 IEEE Std 1003.1-2024<br>
25 Copyright © 2001-2024 The IEEE and The Open Group</font></center>
26 <hr size="2" noshade>
27 <a name="top" id="top"></a> <a name="talk" id="talk"></a> <a name="tag_20_119" id="tag_20_119"></a><!-- talk -->
28 <h4 class="mansect"><a name="tag_20_119_01" id="tag_20_119_01"></a>NAME</h4>
29 <blockquote>talk — talk to another user</blockquote>
30 <h4 class="mansect"><a name="tag_20_119_02" id="tag_20_119_02"></a>SYNOPSIS</h4>
31 <blockquote class="synopsis">
32 <div class="box"><code><tt><sup>[<a href="javascript:open_code('UP')">UP</a>]</sup> <img src="../images/opt-start.gif" alt=
33 "[Option Start]" border="0"> talk</tt> <i>address</i> <b>[</b><i>terminal</i><b>]</b> <tt><img src="../images/opt-end.gif" alt=
34 "[Option End]" border="0"></tt></code></div>
35 </blockquote>
36 <h4 class="mansect"><a name="tag_20_119_03" id="tag_20_119_03"></a>DESCRIPTION</h4>
37 <blockquote>
38 <p>The <i>talk</i> utility is a two-way, screen-oriented communication program.</p>
39 <p>When first invoked, <i>talk</i> shall send a message similar to:</p>
40 <pre>
41 <tt>Message from <</tt><i>unspecified string</i><tt>>
42 talk: connection requested by </tt><i>your_address</i><tt>
43 talk: respond with: talk </tt><i>your_address</i><tt>
44 </tt></pre>
45 <p>to the specified <i>address</i>. At this point, the recipient of the message can reply by typing:</p>
46 <pre>
47 <tt>talk </tt><i>your_address</i><tt>
48 </tt></pre>
49 <p>Once communication is established, the two parties can type simultaneously, with their output displayed in separate regions of
50 the screen. Characters shall be processed as follows:</p>
51 <ul>
52 <li>
53 <p>Typing the <alert> character shall alert the recipient's terminal.</p>
54 </li>
55 <li>
56 <p>Typing <control>-L shall cause the sender's screen regions to be refreshed.</p>
57 </li>
58 <li>
59 <p>Typing the erase and kill characters shall affect the sender's terminal in the manner described by the <b>termios</b> interface
60 in XBD <a href="../basedefs/V1_chap11.html#tag_11"><i>11. General Terminal Interface</i></a> .</p>
61 </li>
62 <li>
63 <p>Typing the interrupt or end-of-file characters shall terminate the local <i>talk</i> utility. Once the <i>talk</i> session has
64 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
65 terminated and shall be able to do nothing except exit.</p>
66 </li>
67 <li>
68 <p>Typing characters from <i>LC_CTYPE</i> classifications <b>print</b> or <b>space</b> shall cause those characters to be sent to
69 the recipient's terminal.</p>
70 </li>
71 <li>
72 <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
73 processing of additional special control characters and multi-byte or single-byte functions shall be implementation-defined.</p>
74 </li>
75 <li>
76 <p>Typing other non-printable characters shall cause implementation-defined sequences of printable characters to be sent to the
77 recipient's terminal.</p>
78 </li>
79 </ul>
80 <p>Permission to be a recipient of a <i>talk</i> message can be denied or granted by use of the <a href=
81 "../utilities/mesg.html"><i>mesg</i></a> utility. However, a user's privilege may further constrain the domain of accessibility of
82 other users' terminals. The <i>talk</i> utility shall fail when the user lacks appropriate privileges to perform the requested
83 action.</p>
84 <p>Certain block-mode terminals do not have all the capabilities necessary to support the simultaneous exchange of messages
85 required for <i>talk</i>. When this type of exchange cannot be supported on such terminals, the implementation may support an
86 exchange with reduced levels of simultaneous interaction or it may report an error describing the terminal-related deficiency.</p>
87 </blockquote>
88 <h4 class="mansect"><a name="tag_20_119_04" id="tag_20_119_04"></a>OPTIONS</h4>
89 <blockquote>
90 <p>None.</p>
91 </blockquote>
92 <h4 class="mansect"><a name="tag_20_119_05" id="tag_20_119_05"></a>OPERANDS</h4>
93 <blockquote>
94 <p>The following operands shall be supported:</p>
95 <dl compact>
96 <dd></dd>
97 <dt><i>address</i></dt>
98 <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
99 <a href="../utilities/who.html"><i>who</i></a> utility. Other address formats and how they are handled are unspecified.</dd>
100 <dt><i>terminal</i></dt>
101 <dd>If the recipient is logged in more than once, the <i>terminal</i> argument can be used to indicate the appropriate terminal
102 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
103 the recipient. The format of <i>terminal</i> shall be the same as that returned by the <a href=
104 "../utilities/who.html"><i>who</i></a> utility.</dd>
105 </dl>
106 </blockquote>
107 <h4 class="mansect"><a name="tag_20_119_06" id="tag_20_119_06"></a>STDIN</h4>
108 <blockquote>
109 <p>Characters read from standard input shall be copied to the recipient's terminal in an unspecified manner. If standard input is
110 not a terminal, talk shall write a diagnostic message and exit with a non-zero status.</p>
111 </blockquote>
112 <h4 class="mansect"><a name="tag_20_119_07" id="tag_20_119_07"></a>INPUT FILES</h4>
113 <blockquote>
114 <p>None.</p>
115 </blockquote>
116 <h4 class="mansect"><a name="tag_20_119_08" id="tag_20_119_08"></a>ENVIRONMENT VARIABLES</h4>
117 <blockquote>
118 <p>The following environment variables shall affect the execution of <i>talk</i>:</p>
119 <dl compact>
120 <dd></dd>
121 <dt><i>LANG</i></dt>
122 <dd>Provide a default value for the internationalization variables that are unset or null. (See XBD <a href=
123 "../basedefs/V1_chap08.html#tag_08_02"><i>8.2 Internationalization Variables</i></a> for the precedence of internationalization
124 variables used to determine the values of locale categories.)</dd>
125 <dt><i>LC_ALL</i></dt>
126 <dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
127 <dt><i>LC_CTYPE</i></dt>
128 <dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
129 opposed to multi-byte characters in arguments and input files). If the recipient's locale does not use an <i>LC_CTYPE</i>
130 equivalent to the sender's, the results are undefined.</dd>
131 <dt><i>LC_MESSAGES</i></dt>
132 <dd><br>
133 Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and
134 informative messages written to standard output.</dd>
135 <dt><i>NLSPATH</i></dt>
136 <dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
137 Determine the location of messages objects and message catalogs. <img src="../images/opt-end.gif" alt="[Option End]" border=
138 "0"></dd>
139 <dt><i>TERM</i></dt>
140 <dd>Determine the name of the invoker's terminal type. If this variable is unset or null, an unspecified default terminal type
141 shall be used.</dd>
142 </dl>
143 </blockquote>
144 <h4 class="mansect"><a name="tag_20_119_09" id="tag_20_119_09"></a>ASYNCHRONOUS EVENTS</h4>
145 <blockquote>
146 <p>When the <i>talk</i> utility receives a SIGINT signal, the utility shall terminate and exit with a zero status. It shall take
147 the standard action for all other signals.</p>
148 </blockquote>
149 <h4 class="mansect"><a name="tag_20_119_10" id="tag_20_119_10"></a>STDOUT</h4>
150 <blockquote>
151 <p>If standard output is a terminal, characters copied from the recipient's standard input may be written to standard output.
152 Standard output also may be used for diagnostic messages. If standard output is not a terminal, <i>talk</i> shall exit with a
153 non-zero status.</p>
154 </blockquote>
155 <h4 class="mansect"><a name="tag_20_119_11" id="tag_20_119_11"></a>STDERR</h4>
156 <blockquote>
157 <p>None.</p>
158 </blockquote>
159 <h4 class="mansect"><a name="tag_20_119_12" id="tag_20_119_12"></a>OUTPUT FILES</h4>
160 <blockquote>
161 <p>None.</p>
162 </blockquote>
163 <h4 class="mansect"><a name="tag_20_119_13" id="tag_20_119_13"></a>EXTENDED DESCRIPTION</h4>
164 <blockquote>
165 <p>None.</p>
166 </blockquote>
167 <h4 class="mansect"><a name="tag_20_119_14" id="tag_20_119_14"></a>EXIT STATUS</h4>
168 <blockquote>
169 <p>The following exit values shall be returned:</p>
170 <dl compact>
171 <dd></dd>
172 <dt> 0</dt>
173 <dd>Successful completion.</dd>
174 <dt>>0</dt>
175 <dd>An error occurred or <i>talk</i> was invoked on a terminal incapable of supporting it.</dd>
176 </dl>
177 </blockquote>
178 <h4 class="mansect"><a name="tag_20_119_15" id="tag_20_119_15"></a>CONSEQUENCES OF ERRORS</h4>
179 <blockquote>
180 <p>Default.</p>
181 </blockquote>
182 <hr>
183 <div class="box"><em>The following sections are informative.</em></div>
184 <h4 class="mansect"><a name="tag_20_119_16" id="tag_20_119_16"></a>APPLICATION USAGE</h4>
185 <blockquote>
186 <p>Because the handling of non-printable, non-<space> characters is tied to the <a href=
187 "../utilities/stty.html"><i>stty</i></a> description of <b>iexten</b>, implementation extensions within the terminal driver can be
188 accessed. For example, some implementations provide line editing functions with certain control character sequences.</p>
189 </blockquote>
190 <h4 class="mansect"><a name="tag_20_119_17" id="tag_20_119_17"></a>EXAMPLES</h4>
191 <blockquote>
192 <p>None.</p>
193 </blockquote>
194 <h4 class="mansect"><a name="tag_20_119_18" id="tag_20_119_18"></a>RATIONALE</h4>
195 <blockquote>
196 <p>The <a href="../utilities/write.html"><i>write</i></a> utility was included in this volume of POSIX.1-2024 since it can be
197 implemented on all terminal types. The <i>talk</i> utility, which cannot be implemented on certain terminals, was considered to be
198 a "better" communications interface. Both of these programs are in widespread use on historical implementations. Therefore, both
199 utilities have been specified.</p>
200 <p>All references to networking abilities (<i>talk</i>ing to a user on another system) were removed as being outside the scope of
201 this volume of POSIX.1-2024.</p>
202 <p>Historical BSD and System V versions of <i>talk</i> terminate both of the conversations when either user breaks out of the
203 session. This can lead to adverse consequences if a user unwittingly continues to enter text that is interpreted by the shell when
204 the other terminates the session. Therefore, the version of <i>talk</i> specified by this volume of POSIX.1-2024 requires both
205 users to terminate their end of the session explicitly.</p>
206 <p>Only messages sent to the terminal of the invoking user can be internationalized in any way:</p>
207 <ul>
208 <li>
209 <p>The original "Message from <<i>unspecified string</i>> ..." message sent to the terminal of the recipient cannot be
210 internationalized because the environment of the recipient is as yet inaccessible to the <i>talk</i> utility. The environment of
211 the invoking party is irrelevant.</p>
212 </li>
213 <li>
214 <p>Subsequent communication between the two parties cannot be internationalized because the two parties may specify different
215 languages in their environment (and non-portable characters cannot be mapped from one language to another).</p>
216 </li>
217 <li>
218 <p>Neither party can be required to communicate in a language other than C and/or the one specified by their environment because
219 unavailable terminal hardware support (for example, fonts) may be required.</p>
220 </li>
221 </ul>
222 <p>The text in the STDOUT section reflects the usage of the verb "display" in this section; some <i>talk</i> implementations
223 actually use standard output to write to the terminal, but this volume of POSIX.1-2024 does not require that to be the case.</p>
224 <p>The format of the terminal name is unspecified, but the descriptions of <a href="../utilities/ps.html"><i>ps</i></a>,
225 <i>talk</i>, <a href="../utilities/who.html"><i>who</i></a>, and <a href="../utilities/write.html"><i>write</i></a> require that
226 they all use or accept the same format.</p>
227 <p>The handling of non-printable characters is partially implementation-defined because the details of mapping them to printable
228 sequences is not needed by the user. Historical implementations, for security reasons, disallow the transmission of non-printable
229 characters that may send commands to the other terminal.</p>
230 </blockquote>
231 <h4 class="mansect"><a name="tag_20_119_19" id="tag_20_119_19"></a>FUTURE DIRECTIONS</h4>
232 <blockquote>
233 <p>None.</p>
234 </blockquote>
235 <h4 class="mansect"><a name="tag_20_119_20" id="tag_20_119_20"></a>SEE ALSO</h4>
236 <blockquote>
237 <p><a href="../utilities/mesg.html#"><i>mesg</i></a> , <a href="../utilities/stty.html#"><i>stty</i></a> , <a href=
238 "../utilities/who.html#"><i>who</i></a> , <a href="../utilities/write.html#tag_20_151"><i>write</i></a></p>
239 <p>XBD <a href="../basedefs/V1_chap08.html#tag_08"><i>8. Environment Variables</i></a> , <a href=
240 "../basedefs/V1_chap11.html#tag_11"><i>11. General Terminal Interface</i></a></p>
241 </blockquote>
242 <h4 class="mansect"><a name="tag_20_119_21" id="tag_20_119_21"></a>CHANGE HISTORY</h4>
243 <blockquote>
244 <p>First released in Issue 4.</p>
245 </blockquote>
246 <h4 class="mansect"><a name="tag_20_119_22" id="tag_20_119_22"></a>Issue 6</h4>
247 <blockquote>
248 <p>This utility is marked as part of the User Portability Utilities option.</p>
249 </blockquote>
250 <h4 class="mansect"><a name="tag_20_119_23" id="tag_20_119_23"></a>Issue 8</h4>
251 <blockquote>
252 <p>Austin Group Defect 1122 is applied, changing the description of <i>NLSPATH .</i></p>
253 </blockquote>
254 <div class="box"><em>End of informative text.</em></div>
255 <hr>
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