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Linux 2.6 - man page for talk (linux section 1posix)

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

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  fol-
       lows:

	* 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  ses-
	  sion	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  char-
	  acters 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 lev-
       els 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 mes-
	      sage  shall  be displayed on one or more accessible terminals in use by the recipi-
	      ent. 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, Inter-
	      nationalization 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 interna-
	      tionalization 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 argu-
	      ments and input files). If the recipient's locale does not use an LC_CTYPE  equiva-
	      lent to the sender's, the results are undefined.

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic messages written to standard error and informative messages written to stan-
	      dard 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  mes-
       sages. 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 cer-
       tain 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 termi-
       nates  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 exam-
	  ple, 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  charac-
       ters 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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  TALK(P)


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