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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 differ (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 simultane-
       ously, with their output displayed in separate 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  ter-
          minal  in  the manner described by the termios interface in the Base
          Definitions volume of IEEE Std 1003.1-2001, Chapter 11, General Ter-
          minal 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  exis-
          tence  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 recipi-
          ent'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 simulta-
       neous 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 utility. Other address  for-
              mats and how they are handled are unspecified.
       terminal
              If the recipient is logged in more than once, the terminal argu-
              ment can be used to indicate the appropriate 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  Vari-
              ables  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 .
       TERM   Determine the name of the invoker's terminal type. If this vari-
              able  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  ter-
       minate  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  recipi-
       ent's  standard input may be written to standard output.  Standard out-
       put 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 termi-
       nal 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 terminal 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.  Therefore, both utili-
       ties 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 con-
       versations when either user breaks out of the session. This can lead to
       adverse consequences if a user unwittingly continues to enter text that
       is  interpreted  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 interna-
       tionalized 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  interna-
          tionalized  because  the two parties may specify different languages
          in their environment (and non-portable characters cannot  be  mapped
          from one language 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 implementations 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 rea-
       sons, disallow 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, 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 .

IEEE/The Open Group                  2003                             TALK(1P)