WRITE(1)                   POSIX Programmer's Manual                  WRITE(1)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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
       delimited by an NL, EOF, or EOL special character (see the Base
       Definitions volume of POSIX.1-2017, 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
           terminal in the manner described by the termios interface in the
           Base Definitions volume of POSIX.1-2017, 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 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
           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 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 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
                 written. 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
                 variables that are unset or null. (See the Base Definitions
                 volume of POSIX.1-2017, 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.

       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
       utility on full-screen terminals.

EXAMPLES
       None.

RATIONALE
       The write utility was included in this volume of POSIX.1-2017 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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mesg, talk, who

       The Base Definitions volume of POSIX.1-2017, Chapter _8, Environment
       Variables, Chapter 11, General Terminal Interface

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             WRITE(1)
