1WRITE(1P) POSIX Programmer's Manual WRITE(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 write — write to another user
13
15 write user_name [terminal]
16
18 The write utility shall read lines from the standard input and write
19 them to the terminal of the specified user. When first invoked, it
20 shall write the message:
21 Message from sender-login-id (sending-terminal) [date]...
24 to user_name. When it has successfully completed the connection, the
26 sender's terminal shall be alerted twice to indicate that what the
27 sender is typing is being written to the recipient's terminal.
28 If the recipient wants to reply, this can be accomplished by typing:
30 write sender-login-id [sending-terminal]
33 upon receipt of the initial message. Whenever a line of input as delim‐
35 ited by an NL, EOF, or EOL special character (see the Base Definitions
36 volume of POSIX.1‐2017, Chapter 11, General Terminal Interface) is
37 accumulated while in canonical input mode, the accumulated data shall
38 be written on the other user's terminal. Characters shall be processed
39 as follows:
40 * Typing <alert> shall write the <alert> character to the recipient's
42 terminal.
43 * Typing the erase and kill characters shall affect the sender's ter‐
45 minal in the manner described by the termios interface in the Base
46 Definitions volume of POSIX.1‐2017, Chapter 11, General Terminal
47 Interface.
48 * Typing the interrupt or end-of-file characters shall cause write to
50 write an appropriate message ("EOT\n" in the POSIX locale) to the
51 recipient's terminal and exit.
52 * Typing characters from LC_CTYPE classifications print or space
54 shall cause those characters to be sent to the recipient's termi‐
55 nal.
56 * When and only when the stty iexten local mode is enabled, the exis‐
58 tence and processing of additional special control characters and
59 multi-byte or single-byte functions is implementation-defined.
60 * Typing other non-printable characters shall cause implementation-
62 defined sequences of printable characters to be written to the
63 recipient's terminal.
64 To write to a user who is logged in more than once, the terminal argu‐
66 ment can be used to indicate which terminal to write to; otherwise, the
67 recipient's terminal is selected in an implementation-defined manner
68 and an informational message is written to the sender's standard out‐
69 put, indicating which terminal was chosen.
70 Permission to be a recipient of a write message can be denied or
72 granted by use of the mesg utility. However, a user's privilege may
73 further constrain the domain of accessibility of other users' termi‐
74 nals. The write utility shall fail when the user lacks appropriate
75 privileges to perform the requested action.
76
78 None.
79
81 The following operands shall be supported:
82 user_name Login name of the person to whom the message shall be writ‐
84 ten. The application shall ensure that this operand is of the
85 form returned by the who utility.
86 terminal Terminal identification in the same format provided by the
88 who utility.
89
91 Lines to be copied to the recipient's terminal are read from standard
92 input.
93
95 None.
96
98 The following environment variables shall affect the execution of
99 write:
100 LANG Provide a default value for the internationalization vari‐
102 ables that are unset or null. (See the Base Definitions vol‐
103 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
104 ables for the precedence of internationalization variables
105 used to determine the values of locale categories.)
106 LC_ALL If set to a non-empty string value, override the values of
108 all the other internationalization variables.
109 LC_CTYPE Determine the locale for the interpretation of sequences of
111 bytes of text data as characters (for example, single-byte as
112 opposed to multi-byte characters in arguments and input
113 files). If the recipient's locale does not use an LC_CTYPE
114 equivalent to the sender's, the results are undefined.
115 LC_MESSAGES
117 Determine the locale that should be used to affect the format
118 and contents of diagnostic messages written to standard error
119 and informative messages written to standard output.
120 NLSPATH Determine the location of message catalogs for the processing
122 of LC_MESSAGES.
123
125 If an interrupt signal is received, write shall write an appropriate
126 message on the recipient's terminal and exit with a status of zero. It
127 shall take the standard action for all other signals.
128
130 An informational message shall be written to standard output if a
131 recipient is logged in more than once.
132
134 The standard error shall be used only for diagnostic messages.
135
137 The recipient's terminal is used for output.
138
140 None.
141
143 The following exit values shall be returned:
144 0 Successful completion.
146 >0 The addressed user is not logged on or the addressed user denies
148 permission.
149
151 Default.
152 The following sections are informative.
154
156 The talk utility is considered by some users to be a more usable util‐
157 ity on full-screen terminals.
158
160 None.
161
163 The write utility was included in this volume of POSIX.1‐2017 since it
164 can be implemented on all terminal types. The standard developers con‐
165 sidered the talk utility, which cannot be implemented on certain termi‐
166 nals, to be a ``better'' communications interface. Both of these pro‐
167 grams are in widespread use on historical implementations. Therefore,
168 the standard developers decided that both utilities should be speci‐
169 fied.
170 The format of the terminal name is unspecified, but the descriptions of
172 ps, talk, who, and write require that they all use or accept the same
173 format.
174
176 None.
177
179 mesg, talk, who
180 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
182 Variables, Chapter 11, General Terminal Interface
183
185 Portions of this text are reprinted and reproduced in electronic form
186 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
187 table Operating System Interface (POSIX), The Open Group Base Specifi‐
188 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
189 Electrical and Electronics Engineers, Inc and The Open Group. In the
190 event of any discrepancy between this version and the original IEEE and
191 The Open Group Standard, the original IEEE and The Open Group Standard
192 is the referee document. The original Standard can be obtained online
193 at http://www.opengroup.org/unix/online.html .
194 Any typographical or formatting errors that appear in this page are
196 most likely to have been introduced during the conversion of the source
197 files to man page format. To report such errors, see https://www.ker‐
198 nel.org/doc/man-pages/reporting_bugs.html .
199IEEE/The Open Group 2017 WRITE(1P)