WRITE(1P) POSIX Programmer's Manual WRITE(1P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAME
write -- write to another user
SYNOPSIS
write user_name [terminal]
DESCRIPTION
The write utility shall read lines from the standard input and write
them to the terminal of the specified user. When first invoked, it
shall write the message:
Message from sender-login-id (sending-terminal) [date]...
to user_name. When it has successfully completed the connection, the
sender's terminal shall be alerted twice to indicate that what the
sender is typing is being written to the recipient's terminal.
If the recipient wants to reply, this can be accomplished by typing:
write sender-login-id [sending-terminal]
upon receipt of the initial message. Whenever a line of input as delim-
ited by an NL, EOF, or EOL special character (see the Base Definitions
volume of POSIX.1-2008, Chapter 11, General Terminal Interface) is
accumulated while in canonical input mode, the accumulated data shall
be written on the other user's terminal. Characters shall be processed
as follows:
* Typing <alert> shall write the <alert> character to the recipient's
terminal.
* Typing the erase and kill characters shall affect the sender's ter-
minal in the manner described by the termios interface in the Base
Definitions volume of POSIX.1-2008, Chapter 11, General Terminal
Interface.
* Typing the interrupt or end-of-file characters shall cause write to
write an appropriate message ("EOT\n" in the POSIX locale) to the
recipient's terminal and exit.
* Typing characters from LC_CTYPE classifications print or space
shall cause those characters to be sent to the recipient's termi-
nal.
* When and only when the stty iexten local mode is enabled, the exis-
tence and processing of additional special control characters and
multi-byte or single-byte functions is implementation-defined.
* Typing other non-printable characters shall cause implementation-
defined sequences of printable characters to be written to the
recipient's terminal.
To write to a user who is logged in more than once, the terminal argu-
ment can be used to indicate which terminal to write to; otherwise, the
recipient's terminal is selected in an implementation-defined manner
and an informational message is written to the sender's standard out-
put, indicating which terminal was chosen.
Permission to be a recipient of a write message can be denied or
granted by use of the mesg utility. However, a user's privilege may
further constrain the domain of accessibility of other users' termi-
nals. The write utility shall fail when the user lacks appropriate
privileges to perform the requested action.
OPTIONS
None.
OPERANDS
The following operands shall be supported:
user_name Login name of the person to whom the message shall be writ-
ten. The application shall ensure that this operand is of the
form returned by the who utility.
terminal Terminal identification in the same format provided by the
who utility.
STDIN
Lines to be copied to the recipient's terminal are read from standard
input.
INPUT FILES
None.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of
write:
LANG Provide a default value for the internationalization vari-
ables that are unset or null. (See the Base Definitions vol-
ume of POSIX.1-2008, Section 8.2, Internationalization Vari-
ables for the precedence of internationalization variables
used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input
files). If the recipient's locale does not use an LC_CTYPE
equivalent to the sender's, the results are undefined.
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error
and informative messages written to standard output.
NLSPATH Determine the location of message catalogs for the processing
of LC_MESSAGES.
ASYNCHRONOUS EVENTS
If an interrupt signal is received, write shall write an appropriate
message on the recipient's terminal and exit with a status of zero. It
shall take the standard action for all other signals.
STDOUT
An informational message shall be written to standard output if a
recipient is logged in more than once.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
The recipient's terminal is used for output.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 The addressed user is not logged on or the addressed user denies
permission.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The talk utility is considered by some users to be a more usable util-
ity on full-screen terminals.
EXAMPLES
None.
RATIONALE
The write utility was included in this volume of POSIX.1-2008 since it
can be implemented on all terminal types. The standard developers con-
sidered the talk utility, which cannot be implemented on certain termi-
nals, to be a ``better'' communications interface. Both of these pro-
grams are in widespread use on historical implementations. Therefore,
the standard developers decided that both utilities should be speci-
fied.
The format of the terminal name is unspecified, but the descriptions of
ps, talk, who, and write require that they all use or accept the same
format.
FUTURE DIRECTIONS
None.
SEE ALSO
mesg, talk, who
The Base Definitions volume of POSIX.1-2008, Chapter 8, Environment
Variables, Chapter 11, General Terminal Interface
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 WRITE(1P)
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