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 .