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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  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  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 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 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
              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 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.

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  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 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 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.

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 .