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write - write to another user
write user_name [terminal]
The write utility shall read lines from the user’s standard input and
write them to the terminal of another 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
delimited by an NL, EOF, or EOL special character (see the Base
Definitions volume of IEEE Std 1003.1-2001, 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
* Typing the erase and kill characters shall affect the sender’s
terminal in the manner described by the termios interface in the
Base Definitions volume of IEEE Std 1003.1-2001, Chapter 11, General
* 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 terminal.
* When and only when the stty iexten local mode is enabled, the
existence 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
To write to a user who is logged in more than once, the terminal
argument 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
output, 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’
terminals. The write utility shall fail when the user lacks the
appropriate privileges to perform the requested action.
The following operands shall be supported:
Login name of the person to whom the message shall be written.
The application shall ensure that this operand is of the form
returned by the who utility.
Terminal identification in the same format provided by the who
Lines to be copied to the recipient’s terminal are read from standard
The following environment variables shall affect the execution of
LANG Provide a default value for the internationalization variables
that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables 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.
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.
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.
Determine the location of message catalogs for the processing of
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.
An informational message shall be written to standard output if a
recipient is logged in more than once.
The standard error shall be used only for diagnostic messages.
The recipient’s terminal is used for output.
The following exit values shall be returned:
0 Successful completion.
>0 The addressed user is not logged on or the addressed user denies
CONSEQUENCES OF ERRORS
The following sections are informative.
The talk utility is considered by some users to be a more usable
utility on full-screen terminals.
The write utility was included in this volume of IEEE Std 1003.1-2001
since it can be implemented on all terminal types. The standard
developers considered the talk utility, which cannot be implemented on
certain terminals, to be a "better" communications interface. Both of
these programs are in widespread use on historical implementations.
Therefore, the standard developers decided that both utilities should
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
mesg , talk , who , the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .