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talk - talk to another user
talk address [terminal]
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:
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
* 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
* 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
* 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-
* Typing other non-printable characters shall cause implementation-
defined sequences of printable characters to be sent to the
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
The following operands shall be supported:
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.
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.
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.
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.
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.
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.
Determine the location of message catalogs for the processing of
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.
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.
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.
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred or talk was invoked on a terminal incapable of
CONSEQUENCES OF ERRORS
The following sections are informative.
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
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
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
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
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.
mesg , stty , who , write , the Base Definitions volume of
IEEE Std 1003.1-2001, Chapter 11, General Terminal Interface
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 .