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 (con-
       sult 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 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 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 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 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 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  defi-
       ciency.

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 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 appropriate termi-
              nal 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 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 .

       TERM   Determine the name of the invoker's terminal type. If this variable is unset or null, an unspecified default  ter-
              minal 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  standard  out-
       put.   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 terminal  types.
       The talk utility, which cannot be implemented on certain terminals, was considered to be a "better" communications inter-
       face. Both of these programs are in widespread use on historical implementations.  Therefore, 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  ses-
       sion.  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 internationalized in any way:

        * The  original "Message from <unspecified string> ..." message sent to the terminal of the recipient cannot be interna-
          tionalized 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 dif-
          ferent 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 actu-
       ally 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, disallow the transmis-
       sion 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, 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                                                      TALK(1P)