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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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WRITE(1P) POSIX Programmer's Manual WRITE(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.
write — write to another user
write user_name [terminal]
The write utility shall read lines from the standard input and
write them to the terminal of the specified user. When first
invoked, it shall write the message:
Message from sender-login-id (sending-terminal) [date]...
to user_name. When it has successfully completed the connection,
the sender's terminal shall be alerted twice to indicate that what
the sender is typing is being written to the recipient's terminal.
If the recipient wants to reply, this can be accomplished by
typing:
write sender-login-id [sending-terminal]
upon receipt of the initial message. Whenever a line of input as
delimited by an NL, EOF, or EOL special character (see the Base
Definitions volume of POSIX.1‐2017, Chapter 11, General Terminal
Interface) is accumulated while in canonical input mode, the
accumulated data shall be written on the other user's terminal.
Characters shall be processed as follows:
* Typing <alert> shall write the <alert> character to the
recipient's terminal.
* 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 cause
write to write an appropriate message ("EOT\n" in the POSIX
locale) to the recipient's terminal and 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 is
implementation-defined.
* Typing other non-printable characters shall cause
implementation-defined sequences of printable characters to be
written to the recipient's terminal.
To write to a user who is logged in more than once, the terminal
argument can be used to indicate which terminal to write to;
otherwise, the recipient's terminal is selected in an
implementation-defined manner and an informational message is
written to the sender's standard output, indicating which terminal
was chosen.
Permission to be a recipient of a write 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 write utility shall fail when the user lacks
appropriate privileges to perform the requested action.
None.
The following operands shall be supported:
user_name Login name of the person to whom the message shall be
written. The application shall ensure that this operand
is of the form returned by the who utility.
terminal Terminal identification in the same format provided by
the who utility.
Lines to be copied to the recipient's terminal are read from
standard input.
None.
The following environment variables shall affect the execution of
write:
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.
If an interrupt signal is received, write shall write an
appropriate message on the recipient's terminal and exit with a
status of zero. It shall take the standard action for all other
signals.
An informational message shall be written to standard output if a
recipient is logged in more than once.
The standard error shall be used only for diagnostic messages.
The recipient's terminal is used for output.
None.
The following exit values shall be returned:
0 Successful completion.
>0 The addressed user is not logged on or the addressed user
denies permission.
Default.
The following sections are informative.
The talk utility is considered by some users to be a more usable
utility on full-screen terminals.
None.
The write utility was included in this volume of POSIX.1‐2017
since it can be implemented on all terminal types. The standard
developers considered the talk utility, which cannot be
implemented on certain terminals, to be a ``better''
communications interface. Both of these programs are in widespread
use on historical implementations. Therefore, the standard
developers decided that both utilities should be specified.
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.
None.
mesg(1p), talk(1p), who(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 WRITE(1P)
Pages that refer to this page: logger(1p), mesg(1p), talk(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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