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TALK(1P)                   POSIX Programmer's Manual                  TALK(1P)



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

NAME
       talk - talk to another user

SYNOPSIS
       talk address [terminal]

DESCRIPTION
       The talk utility is a two-way, screen-oriented communication program.

       When first invoked, talk shall send a message similar to:


              Message from <unspecified string>
              talk: connection requested by your_addresstalk: respond with: talk your_address

       to the specified address. At this point, the recipient of the message can reply by typing:


              talk your_address

       Once communication is established, the two parties can type simultaneously, with their output displayed in sep-
       arate regions of the screen. Characters shall be processed as follows:

        * Typing the alert character shall alert the recipient's terminal.


        * Typing <control>-L shall cause the sender's screen regions to be refreshed.


        * 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 terminate the local talk utility. Once the talk session
          has  been terminated on one side, the other side of the talk session shall be notified that the talk session
          has been terminated and shall be able to do nothing except 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 shall be implementation-defined.


        * Typing other non-printable characters shall cause implementation-defined sequences of  printable  characters
          to be sent to the recipient's terminal.


       Permission  to be a recipient of a talk 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 talk  utility
       shall fail when the user lacks the appropriate privileges to perform the requested action.

       Certain block-mode terminals do not have all the capabilities necessary to support the simultaneous exchange of
       messages required  for  talk.  When  this  type  of  exchange  cannot  be  supported  on  such  terminals,  the
       implementation  may  support  an  exchange  with reduced levels of simultaneous interaction or it may report an
       error describing the terminal-related deficiency.

OPTIONS
       None.

OPERANDS
       The following operands shall be supported:

       address
              The recipient of the talk session. One form of address is the <user name>, as returned by the who  util-
              ity. Other address formats and how they are handled are unspecified.

       terminal
              If  the  recipient is logged in more than once, the terminal argument can be used to indicate the appro-
              priate terminal name. If terminal is not specified, the talk message shall be displayed on one  or  more
              accessible  terminals in use by the recipient. The format of terminal shall be the same as that returned
              by the who utility.


STDIN
       Characters read from standard input shall be copied to the recipient's terminal in an  unspecified  manner.  If
       standard input is not a terminal, talk shall write a diagnostic message and exit with a non-zero status.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of talk:

       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  prece-
              dence 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  exam-
              ple,  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  writ-
              ten to standard error and informative messages written to standard output.

       NLSPATH
              Determine the location of message catalogs for the processing of LC_MESSAGES .

       TERM   Determine  the  name  of  the invoker's terminal type. If this variable is unset or null, an unspecified
              default terminal type shall be used.


ASYNCHRONOUS EVENTS
       When the talk utility receives a SIGINT signal, the utility shall terminate and exit with  a  zero  status.  It
       shall take the standard action for all other signals.

STDOUT
       If standard output is a terminal, characters copied from the recipient's standard input may be written to stan-
       dard output.  Standard output also may be used for diagnostic messages. If standard output is not  a  terminal,
       talk shall exit with a non-zero status.

STDERR
       None.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       The following exit values shall be returned:

        0     Successful completion.

       >0     An error occurred or talk was invoked on a terminal incapable of supporting it.


CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       Because  the handling of non-printable, non- <space>s is tied to the stty description of iexten, implementation
       extensions within the terminal driver can be accessed. For example, some implementations provide  line  editing
       functions with certain control character sequences.

EXAMPLES
       None.

RATIONALE
       The write utility was included in this volume of IEEE Std 1003.1-2001 since it can be implemented on all termi-
       nal types. The talk utility, which cannot be implemented on certain terminals, was considered to be a  "better"
       communications  interface.  Both of these programs are in widespread use on historical implementations.  There-
       fore, both utilities have been specified.

       All references to networking abilities (talking to a user on another system) were removed as being outside  the
       scope of this volume of IEEE Std 1003.1-2001.

       Historical BSD and System V versions of talk terminate both of the conversations when either user breaks out of
       the session. This can lead to adverse consequences if a user unwittingly continues to enter text that is inter-
       preted  by  the  shell  when the other terminates the session. Therefore, the version of talk specified by this
       volume of IEEE Std 1003.1-2001 requires both users to terminate their end of the session explicitly.

       Only messages sent to the terminal of the invoking user can be internationalized in any way:

        * The original "Message from <unspecified string> ..." message sent to the terminal of the recipient cannot be
          internationalized  because  the environment of the recipient is as yet inaccessible to the talk utility. The
          environment of the invoking party is irrelevant.


        * Subsequent communication between the two parties cannot be internationalized because  the  two  parties  may
          specify different languages in their environment (and non-portable characters cannot be mapped from one lan-
          guage to another).


        * Neither party can be required to communicate in a language other than C and/or the one  specified  by  their
          environment because unavailable terminal hardware support (for example, fonts) may be required.


       The  text in the STDOUT section reflects the usage of the verb "display" in this section; some talk implementa-
       tions actually use standard output to write to the terminal, but this volume of IEEE Std 1003.1-2001  does  not
       require that to be the case.

       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.

       The handling of non-printable characters is partially implementation-defined because  the  details  of  mapping
       them to printable sequences is not needed by the user. Historical implementations, for security reasons, disal-
       low the transmission of non-printable characters that may send commands to the other terminal.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mesg, stty, who, write, 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, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                             TALK(1P)