PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

TALK(1P)                  POSIX Programmer's Manual                 TALK(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior), or
       the interface may not be implemented on Linux.

NAME         top

       talk — talk to another user

SYNOPSIS         top

       talk address [terminal]

DESCRIPTION         top

       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_address
           talk: 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 POSIX.1‐2008, 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
       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         top

       None.

OPERANDS         top

       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         top

       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         top

       None.

ENVIRONMENT VARIABLES         top

       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 POSIX.1‐2008, 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         top

       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         top

       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         top

       None.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       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         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       Because the handling of non-printable, non-<space> characters 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         top

       None.

RATIONALE         top

       The write utility was included in this volume of POSIX.1‐2008 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
       POSIX.1‐2008.

       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
       POSIX.1‐2008 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
       POSIX.1‐2008 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         top

       None.

SEE ALSO         top

       mesg(1p), stty(1p), who(1p), write(1p)

       The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
       Variables, Chapter 11, General Terminal Interface

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                            TALK(1P)

Pages that refer to this page: mesg(1p)write(1p)