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23 <script language="JavaScript" src="../jscript/codes.js"></script><basefont size="3">
24 <center><font size="2">The Open Group Base Specifications Issue 8<br>
25 IEEE Std 1003.1-2024<br>
26 Copyright © 2001-2024 The IEEE and The Open Group</font></center>
27 <hr size="2" noshade>
28 <a name="top" id="top"></a> <a name="write" id="write"></a> <a name="tag_20_151" id="tag_20_151"></a><!-- write -->
29 <h4 class="mansect"><a name="tag_20_151_01" id="tag_20_151_01"></a>NAME</h4>
30 <blockquote>write — write to another user</blockquote>
31 <h4 class="mansect"><a name="tag_20_151_02" id="tag_20_151_02"></a>SYNOPSIS</h4>
32 <blockquote class="synopsis">
33 <p><code><tt>write</tt> <i>user_name</i> <b>[</b><i>terminal</i><b>]</b></code></p>
34 </blockquote>
35 <h4 class="mansect"><a name="tag_20_151_03" id="tag_20_151_03"></a>DESCRIPTION</h4>
36 <blockquote>
37 <p>The <i>write</i> utility shall read lines from the standard input and write them to the terminal of the specified user. When
38 first invoked, it shall write the message:</p>
39 <pre>
40 <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>...
41 </tt></pre>
42 <p>to <i>user_name</i>. When it has successfully completed the connection, the sender's terminal shall be alerted twice to indicate
43 that what the sender is typing is being written to the recipient's terminal.</p>
44 <p>If the recipient wants to reply, this can be accomplished by typing:</p>
45 <pre>
46 <tt>write </tt><i>sender-login-id </i><b>[</b><i>sending-terminal</i><b>]</b><tt>
47 </tt></pre>
48 <p>upon receipt of the initial message. Whenever a line of input as delimited by an NL, EOF, or EOL special character (see XBD
49 <a href="../basedefs/V1_chap11.html#tag_11"><i>11. General Terminal Interface</i></a> ) is accumulated while in canonical input
50 mode, the accumulated data shall be written on the other user's terminal. Characters shall be processed as follows:</p>
51 <ul>
52 <li>
53 <p>Typing <alert> shall write the <alert> character to the recipient's terminal.</p>
54 </li>
55 <li>
56 <p>Typing the erase and kill characters shall affect the sender's terminal in the manner described by the <b>termios</b> interface
57 in XBD <a href="../basedefs/V1_chap11.html#tag_11"><i>11. General Terminal Interface</i></a> .</p>
58 </li>
59 <li>
60 <p>Typing the interrupt or end-of-file characters shall cause <i>write</i> to write an appropriate message (<tt>"EOT\n"</tt> in the
61 POSIX locale) to the recipient's terminal and exit.</p>
62 </li>
63 <li>
64 <p>Typing characters from <i>LC_CTYPE</i> classifications <b>print</b> or <b>space</b> shall cause those characters to be sent to
65 the recipient's terminal.</p>
66 </li>
67 <li>
68 <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
69 processing of additional special control characters and multi-byte or single-byte functions is implementation-defined.</p>
70 </li>
71 <li>
72 <p>Typing other non-printable characters shall cause implementation-defined sequences of printable characters to be written to the
73 recipient's terminal.</p>
74 </li>
75 </ul>
76 <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
77 to; otherwise, the recipient's terminal is selected in an implementation-defined manner and an informational message is written to
78 the sender's standard output, indicating which terminal was chosen.</p>
79 <p>Permission to be a recipient of a <i>write</i> message can be denied or granted by use of the <a href=
80 "../utilities/mesg.html"><i>mesg</i></a> utility. However, a user's privilege may further constrain the domain of accessibility of
81 other users' terminals. The <i>write</i> utility shall fail when the user lacks appropriate privileges to perform the requested
82 action.</p>
83 </blockquote>
84 <h4 class="mansect"><a name="tag_20_151_04" id="tag_20_151_04"></a>OPTIONS</h4>
85 <blockquote>
86 <p>None.</p>
87 </blockquote>
88 <h4 class="mansect"><a name="tag_20_151_05" id="tag_20_151_05"></a>OPERANDS</h4>
89 <blockquote>
90 <p><br>
91 The following operands shall be supported:</p>
92 <dl compact>
93 <dd></dd>
94 <dt><i>user_name</i></dt>
95 <dd>Login name of the person to whom the message shall be written. The application shall ensure that this operand is of the form
96 returned by the <a href="../utilities/who.html"><i>who</i></a> utility.</dd>
97 <dt><i>terminal</i></dt>
98 <dd>Terminal identification in the same format provided by the <a href="../utilities/who.html"><i>who</i></a> utility.</dd>
99 </dl>
100 </blockquote>
101 <h4 class="mansect"><a name="tag_20_151_06" id="tag_20_151_06"></a>STDIN</h4>
102 <blockquote>
103 <p>Lines to be copied to the recipient's terminal are read from standard input.</p>
104 </blockquote>
105 <h4 class="mansect"><a name="tag_20_151_07" id="tag_20_151_07"></a>INPUT FILES</h4>
106 <blockquote>
107 <p>None.</p>
108 </blockquote>
109 <h4 class="mansect"><a name="tag_20_151_08" id="tag_20_151_08"></a>ENVIRONMENT VARIABLES</h4>
110 <blockquote>
111 <p>The following environment variables shall affect the execution of <i>write</i>:</p>
112 <dl compact>
113 <dd></dd>
114 <dt><i>LANG</i></dt>
115 <dd>Provide a default value for the internationalization variables that are unset or null. (See XBD <a href=
116 "../basedefs/V1_chap08.html#tag_08_02"><i>8.2 Internationalization Variables</i></a> for the precedence of internationalization
117 variables used to determine the values of locale categories.)</dd>
118 <dt><i>LC_ALL</i></dt>
119 <dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd>
120 <dt><i>LC_CTYPE</i></dt>
121 <dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as
122 opposed to multi-byte characters in arguments and input files). If the recipient's locale does not use an <i>LC_CTYPE</i>
123 equivalent to the sender's, the results are undefined.</dd>
124 <dt><i>LC_MESSAGES</i></dt>
125 <dd><br>
126 Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error and
127 informative messages written to standard output.</dd>
128 <dt><i>NLSPATH</i></dt>
129 <dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
130 Determine the location of messages objects and message catalogs. <img src="../images/opt-end.gif" alt="[Option End]" border=
131 "0"></dd>
132 </dl>
133 </blockquote>
134 <h4 class="mansect"><a name="tag_20_151_09" id="tag_20_151_09"></a>ASYNCHRONOUS EVENTS</h4>
135 <blockquote>
136 <p>If an interrupt signal is received, <i>write</i> shall write an appropriate message on the recipient's terminal and exit with a
137 status of zero. It shall take the standard action for all other signals.</p>
138 </blockquote>
139 <h4 class="mansect"><a name="tag_20_151_10" id="tag_20_151_10"></a>STDOUT</h4>
140 <blockquote>
141 <p>An informational message shall be written to standard output if a recipient is logged in more than once.</p>
142 </blockquote>
143 <h4 class="mansect"><a name="tag_20_151_11" id="tag_20_151_11"></a>STDERR</h4>
144 <blockquote>
145 <p>The standard error shall be used only for diagnostic messages.</p>
146 </blockquote>
147 <h4 class="mansect"><a name="tag_20_151_12" id="tag_20_151_12"></a>OUTPUT FILES</h4>
148 <blockquote>
149 <p>The recipient's terminal is used for output.</p>
150 </blockquote>
151 <h4 class="mansect"><a name="tag_20_151_13" id="tag_20_151_13"></a>EXTENDED DESCRIPTION</h4>
152 <blockquote>
153 <p>None.</p>
154 </blockquote>
155 <h4 class="mansect"><a name="tag_20_151_14" id="tag_20_151_14"></a>EXIT STATUS</h4>
156 <blockquote>
157 <p>The following exit values shall be returned:</p>
158 <dl compact>
159 <dd></dd>
160 <dt> 0</dt>
161 <dd>Successful completion.</dd>
162 <dt>>0</dt>
163 <dd>The addressed user is not logged on or the addressed user denies permission.</dd>
164 </dl>
165 </blockquote>
166 <h4 class="mansect"><a name="tag_20_151_15" id="tag_20_151_15"></a>CONSEQUENCES OF ERRORS</h4>
167 <blockquote>
168 <p>Default.</p>
169 </blockquote>
170 <hr>
171 <div class="box"><em>The following sections are informative.</em></div>
172 <h4 class="mansect"><a name="tag_20_151_16" id="tag_20_151_16"></a>APPLICATION USAGE</h4>
173 <blockquote>
174 <p>The <a href="../utilities/talk.html"><i>talk</i></a> utility is considered by some users to be a more usable utility on
175 full-screen terminals.</p>
176 </blockquote>
177 <h4 class="mansect"><a name="tag_20_151_17" id="tag_20_151_17"></a>EXAMPLES</h4>
178 <blockquote>
179 <p>None.</p>
180 </blockquote>
181 <h4 class="mansect"><a name="tag_20_151_18" id="tag_20_151_18"></a>RATIONALE</h4>
182 <blockquote>
183 <p>The <i>write</i> utility was included in this volume of POSIX.1-2024 since it can be implemented on all terminal types. The
184 standard developers considered the <a href="../utilities/talk.html"><i>talk</i></a> utility, which cannot be implemented on certain
185 terminals, to be a "better" communications interface. Both of these programs are in widespread use on historical implementations.
186 Therefore, the standard developers decided that both utilities should be specified.</p>
187 <p>The format of the terminal name is unspecified, but the descriptions of <a href="../utilities/ps.html"><i>ps</i></a>, <a href=
188 "../utilities/talk.html"><i>talk</i></a>, <a href="../utilities/who.html"><i>who</i></a>, and <i>write</i> require that they all
189 use or accept the same format.</p>
190 </blockquote>
191 <h4 class="mansect"><a name="tag_20_151_19" id="tag_20_151_19"></a>FUTURE DIRECTIONS</h4>
192 <blockquote>
193 <p>None.</p>
194 </blockquote>
195 <h4 class="mansect"><a name="tag_20_151_20" id="tag_20_151_20"></a>SEE ALSO</h4>
196 <blockquote>
197 <p><a href="../utilities/mesg.html#"><i>mesg</i></a> , <a href="../utilities/talk.html#"><i>talk</i></a> , <a href=
198 "../utilities/who.html#"><i>who</i></a></p>
199 <p>XBD <a href="../basedefs/V1_chap08.html#tag_08"><i>8. Environment Variables</i></a> , <a href=
200 "../basedefs/V1_chap11.html#tag_11"><i>11. General Terminal Interface</i></a></p>
201 </blockquote>
202 <h4 class="mansect"><a name="tag_20_151_21" id="tag_20_151_21"></a>CHANGE HISTORY</h4>
203 <blockquote>
204 <p>First released in Issue 2.</p>
205 </blockquote>
206 <h4 class="mansect"><a name="tag_20_151_22" id="tag_20_151_22"></a>Issue 5</h4>
207 <blockquote>
208 <p>The FUTURE DIRECTIONS section is added.</p>
209 </blockquote>
210 <h4 class="mansect"><a name="tag_20_151_23" id="tag_20_151_23"></a>Issue 6</h4>
211 <blockquote>
212 <p>This utility is marked as part of the User Portability Utilities option.</p>
213 <p>The normative text is reworded to avoid use of the term "must" for application requirements.</p>
214 </blockquote>
215 <h4 class="mansect"><a name="tag_20_151_24" id="tag_20_151_24"></a>Issue 7</h4>
216 <blockquote>
217 <p>The <i>write</i> utility is moved from the User Portability Utilities option to the Base. User Portability Utilities is now an
218 option for interactive utilities.</p>
219 </blockquote>
220 <h4 class="mansect"><a name="tag_20_151_25" id="tag_20_151_25"></a>Issue 8</h4>
221 <blockquote>
222 <p>Austin Group Defect 1122 is applied, changing the description of <i>NLSPATH .</i></p>
223 </blockquote>
224 <div class="box"><em>End of informative text.</em></div>
225 <hr>
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