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The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008
Copyright © 2001-2008 The IEEE and The Open Group

#### NAME

> write - write to another user

#### SYNOPSIS

> ``write` user_name [terminal]`

#### DESCRIPTION

> 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 XBD 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 XBD 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.

#### OPTIONS

> None.

#### OPERANDS

> 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.

#### STDIN

> Lines to be copied to the recipient's terminal are read from standard input.

#### INPUT FILES

> None.

#### ENVIRONMENT VARIABLES

> 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 XBD 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
>   [XSI] Determine the location of message catalogs for the processing of LC_MESSAGES .

#### ASYNCHRONOUS EVENTS

> 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.

#### STDOUT

> An informational message shall be written to standard output if a recipient is logged in more than once.

#### STDERR

> The standard error shall be used only for diagnostic messages.

#### OUTPUT FILES

> The recipient's terminal is used for output.

#### EXTENDED DESCRIPTION

> None.

#### EXIT STATUS

> The following exit values shall be returned:

> 0
>   Successful completion.
> >0
>   The addressed user is not logged on or the addressed user denies permission.

#### CONSEQUENCES OF ERRORS

> Default.

The following sections are informative.

#### APPLICATION USAGE

> The talk utility is considered by some users to be a more usable utility on full-screen terminals.

#### EXAMPLES

> None.

#### RATIONALE

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

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> mesg , talk , who

> XBD Environment Variables , General Terminal Interface

#### CHANGE HISTORY

> First released in Issue 2.

#### Issue 5

> The FUTURE DIRECTIONS section is added.

#### Issue 6

> This utility is marked as part of the User Portability Utilities option.

> The normative text is reworded to avoid use of the term "must" for application requirements.

#### Issue 7

> The write utility is moved from the User Portability Utilities option to the Base. User Portability Utilities is now an option for interactive utilities.

End of informative text.

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Copyright © 2001-2008 The IEEE and The Open Group, All Rights Reserved
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