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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 |
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TALK(1P) POSIX Programmer's Manual TALK(1P)
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.
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_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.1‐2017, 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.
None.
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.
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.
None.
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.1‐2017, 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.
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.
None.
None.
None.
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.
Default.
The following sections are informative.
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.
None.
The write utility was included in this volume of POSIX.1‐2017
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.1‐2017.
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.1‐2017 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.1‐2017 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.
None.
mesg(1p), stty(1p), who(1p), write(1p)
The Base Definitions volume of POSIX.1‐2017, Chapter 8,
Environment Variables, Chapter 11, General Terminal Interface
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 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 .
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 2017 TALK(1P)
Pages that refer to this page: mesg(1p), write(1p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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