Ubuntu Manpage: talk - talk to another user

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.

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 .