mirror of https://github.com/mkerrisk/man-pages
220 lines
7.0 KiB
Groff
220 lines
7.0 KiB
Groff
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "WRITE" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" write
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.SH NAME
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write \- write to another user
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.SH SYNOPSIS
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.LP
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\fBwrite\fP \fIuser_name\fP \fB[\fP\fIterminal\fP\fB]\fP\fB\fP
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.SH DESCRIPTION
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.LP
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The \fIwrite\fP utility shall read lines from the user's standard
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input and write them to the terminal of another user. When
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first invoked, it shall write the message:
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.sp
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.RS
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.nf
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\fBMessage from\fP \fIsender-login-id\fP \fB(\fP\fIsending-terminal\fP\fB)\fP \fB[\fP\fIdate\fP\fB]\fP\fB...
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\fP
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.fi
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.RE
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.LP
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to \fIuser_name\fP. When it has successfully completed the connection,
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the sender's terminal shall be alerted twice to indicate
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that what the sender is typing is being written to the recipient's
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terminal.
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.LP
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If the recipient wants to reply, this can be accomplished by typing:
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.sp
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.RS
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.nf
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\fBwrite\fP \fIsender-login-id\fP \fB[\fP\fIsending-terminal\fP\fB]\fP
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.fi
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.RE
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.LP
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upon receipt of the initial message. Whenever a line of input as delimited
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by an NL, EOF, or EOL special character (see the Base
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Definitions volume of IEEE\ Std\ 1003.1-2001, Chapter 11, General
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Terminal
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Interface) is accumulated while in canonical input mode, the accumulated
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data shall be written on the other user's terminal.
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Characters shall be processed as follows:
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.IP " *" 3
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Typing <alert> shall write the alert character to the recipient's
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terminal.
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.LP
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.IP " *" 3
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Typing the erase and kill characters shall affect the sender's terminal
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in the manner described by the \fBtermios\fP interface
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in the Base Definitions volume of IEEE\ Std\ 1003.1-2001, Chapter
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11, General
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Terminal Interface.
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.LP
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.IP " *" 3
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Typing the interrupt or end-of-file characters shall cause \fIwrite\fP
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to write an appropriate message ( \fB"EOT\\n"\fP in
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the POSIX locale) to the recipient's terminal and exit.
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.LP
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.IP " *" 3
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Typing characters from \fILC_CTYPE\fP classifications \fBprint\fP
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or \fBspace\fP shall cause those characters to be sent to
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the recipient's terminal.
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.LP
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.IP " *" 3
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When and only when the \fIstty\fP \fBiexten\fP local mode is enabled,
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the existence and
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processing of additional special control characters and multi-byte
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or single-byte functions is implementation-defined.
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.LP
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.IP " *" 3
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Typing other non-printable characters shall cause implementation-defined
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sequences of printable characters to be written to the
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recipient's terminal.
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.LP
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.LP
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To write to a user who is logged in more than once, the \fIterminal\fP
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argument can be used to indicate which terminal to write
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to; otherwise, the recipient's terminal is selected in an implementation-defined
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manner and an informational message is written to
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the sender's standard output, indicating which terminal was chosen.
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.LP
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Permission to be a recipient of a \fIwrite\fP message can be denied
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or granted by use of the \fImesg\fP utility. However, a user's privilege
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may further constrain the domain of accessibility of
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other users' terminals. The \fIwrite\fP utility shall fail when the
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user lacks the appropriate privileges to perform the requested
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action.
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.SH OPTIONS
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.LP
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None.
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.SH OPERANDS
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.LP
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The following operands shall be supported:
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.TP 7
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\fIuser_name\fP
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Login name of the person to whom the message shall be written. The
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application shall ensure that this operand is of the form
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returned by the \fIwho\fP utility.
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.TP 7
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\fIterminal\fP
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Terminal identification in the same format provided by the \fIwho\fP
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utility.
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.sp
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.SH STDIN
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.LP
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Lines to be copied to the recipient's terminal are read from standard
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input.
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.SH INPUT FILES
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.LP
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None.
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.SH ENVIRONMENT VARIABLES
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.LP
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The following environment variables shall affect the execution of
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\fIwrite\fP:
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.TP 7
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\fILANG\fP
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Provide a default value for the internationalization variables that
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are unset or null. (See the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
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for
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the precedence of internationalization variables used to determine
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the values of locale categories.)
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.TP 7
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\fILC_ALL\fP
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If set to a non-empty string value, override the values of all the
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other internationalization variables.
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.TP 7
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\fILC_CTYPE\fP
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Determine the locale for the interpretation of sequences of bytes
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of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments and input files). If
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the recipient's locale does not use an \fILC_CTYPE\fP
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equivalent to the sender's, the results are undefined.
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.TP 7
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\fILC_MESSAGES\fP
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Determine the locale that should be used to affect the format and
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contents of diagnostic messages written to standard error and
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informative messages written to standard output.
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.TP 7
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\fINLSPATH\fP
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Determine the location of message catalogs for the processing of \fILC_MESSAGES
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\&.\fP
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.sp
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.SH ASYNCHRONOUS EVENTS
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.LP
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If an interrupt signal is received, \fIwrite\fP shall write an appropriate
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message on the recipient's terminal and exit with a
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status of zero. It shall take the standard action for all other signals.
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.SH STDOUT
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.LP
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An informational message shall be written to standard output if a
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recipient is logged in more than once.
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.SH STDERR
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.LP
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The standard error shall be used only for diagnostic messages.
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.SH OUTPUT FILES
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.LP
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The recipient's terminal is used for output.
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.SH EXTENDED DESCRIPTION
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.LP
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None.
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.SH EXIT STATUS
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.LP
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The following exit values shall be returned:
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.TP 7
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\ 0
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Successful completion.
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.TP 7
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>0
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The addressed user is not logged on or the addressed user denies permission.
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.sp
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.SH CONSEQUENCES OF ERRORS
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.LP
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Default.
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.LP
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\fIThe following sections are informative.\fP
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.SH APPLICATION USAGE
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.LP
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The \fItalk\fP utility is considered by some users to be a more usable
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utility on
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full-screen terminals.
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.SH EXAMPLES
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.LP
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None.
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.SH RATIONALE
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.LP
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The \fIwrite\fP utility was included in this volume of IEEE\ Std\ 1003.1-2001
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since it can be implemented on all
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terminal types. The standard developers considered the \fItalk\fP
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utility, which cannot be
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implemented on certain terminals, to be a "better" communications
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interface. Both of these programs are in widespread use on
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historical implementations. Therefore, the standard developers decided
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that both utilities should be specified.
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.LP
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The format of the terminal name is unspecified, but the descriptions
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of \fIps\fP, \fItalk\fP, \fIwho\fP, and \fIwrite\fP require that they
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all
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use or accept the same format.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fImesg\fP , \fItalk\fP , \fIwho\fP , the Base
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Definitions volume of IEEE\ Std\ 1003.1-2001, Chapter 11, General
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Terminal
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Interface
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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