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       talk - talk to another user


       talk address [terminal]


       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

        * 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.




       The following operands shall be supported:

              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

              If  the recipient is logged in more than once, the terminal argument 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


       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.




       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 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.

              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.

              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.

              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.


       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.


       If standard output is a terminal, characters copied from the  recipient's  standard  input
       may  be  written  to  standard  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.








       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.



       The following sections are informative.


       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




       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  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  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

        * 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

        * 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 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  reasons,  disallow  the  transmission  of  non-printable
       characters that may send commands to the other terminal.




       mesg , stty , who , write , the Base Definitions volume of  IEEE Std 1003.1-2001,  Chapter
       11, General Terminal Interface


       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 .