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 (con-
       sult 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 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 terminal.

        * Typing the erase and kill characters shall affect the sender's terminal in the manner described by the termios  inter-
          face 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  recipi-
          ent'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 writ-
          ten 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 the 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  IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of international-
              ization 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 stan-
              dard 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 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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mesg, talk, who, the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface

COPYRIGHT
       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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     WRITE(1P)