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:
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
Typing <alert> shall write the alert character to the
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 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 terminal.
When and only when the sttyiexten local mode
is enabled, the existence and processing of additional special control
characters and multi-byte or single-byte functions is
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 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
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 environment variables shall affect the execution of write:
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.)
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 LC_MESSAGES.
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 be specified.
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.
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