mirror of https://github.com/mkerrisk/man-pages
213 lines
5.6 KiB
Groff
213 lines
5.6 KiB
Groff
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "ALIAS" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" alias
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.SH NAME
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alias \- define or display aliases
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.SH SYNOPSIS
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.LP
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\fBalias\fP \fB[\fP\fIalias-name\fP\fB[\fP\fB=\fP\fIstring\fP\fB]\fP
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\fB\&...\fP\fB]\fP\fB\fP
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.SH DESCRIPTION
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.LP
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The \fIalias\fP utility shall create or redefine alias definitions
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or write the values of existing alias definitions to
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standard output. An alias definition provides a string value that
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shall replace a command name when it is encountered; see \fIAlias
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Substitution\fP .
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.LP
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An alias definition shall affect the current shell execution environment
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and the execution environments of the subshells of the
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current shell. When used as specified by this volume of IEEE\ Std\ 1003.1-2001,
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the alias definition shall not affect the
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parent process of the current shell nor any utility environment invoked
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by the shell; see \fIShell Execution Environment\fP .
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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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\fIalias-name\fP
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Write the alias definition to standard output.
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.TP 7
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\fIalias-name\fP=\fIstring\fP
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.sp
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Assign the value of \fIstring\fP to the alias \fIalias-name\fP.
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.sp
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.LP
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If no operands are given, all alias definitions shall be written to
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standard output.
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.SH STDIN
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.LP
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Not used.
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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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\fIalias\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).
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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
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error.
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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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Default.
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.SH STDOUT
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.LP
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The format for displaying aliases (when no operands or only \fIname\fP
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operands are specified) shall be:
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.sp
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.RS
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.nf
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\fB"%s=%s\\n",\fP \fIname\fP\fB,\fP \fIvalue\fP
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.fi
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.RE
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.LP
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The \fIvalue\fP string shall be written with appropriate quoting so
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that it is suitable for reinput to the shell. See the
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description of shell quoting in \fIQuoting\fP .
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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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None.
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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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One of the \fIname\fP operands specified did not have an alias definition,
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or an error occurred.
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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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None.
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.SH EXAMPLES
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.IP " 1." 4
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Change \fIls\fP to give a columnated, more annotated output:
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.sp
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.RS
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.nf
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\fBalias ls="ls -CF"
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\fP
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.fi
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.RE
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.LP
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.IP " 2." 4
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Create a simple "redo" command to repeat previous entries in the command
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history file:
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.sp
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.RS
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.nf
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\fBalias r='fc -s'
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\fP
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.fi
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.RE
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.LP
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.IP " 3." 4
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Use 1K units for \fIdu\fP:
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.sp
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.RS
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.nf
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\fBalias du=du\\ -k
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\fP
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.fi
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.RE
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.LP
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.IP " 4." 4
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Set up \fInohup\fP so that it can deal with an argument that is itself
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an alias name:
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.sp
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.RS
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.nf
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\fBalias nohup="nohup "
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\fP
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.fi
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.RE
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.LP
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.SH RATIONALE
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.LP
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The \fIalias\fP description is based on historical KornShell implementations.
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Known differences exist between that and the C
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shell. The KornShell version was adopted to be consistent with all
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the other KornShell features in this volume of
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IEEE\ Std\ 1003.1-2001, such as command line editing.
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.LP
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Since \fIalias\fP affects the current shell execution environment,
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it is generally provided as a shell regular built-in.
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.LP
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Historical versions of the KornShell have allowed aliases to be exported
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to scripts that are invoked by the same shell. This is
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triggered by the \fIalias\fP \fB-x\fP flag; it is allowed by this
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volume of IEEE\ Std\ 1003.1-2001 only when an explicit
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extension such as \fB-x\fP is used. The standard developers considered
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that aliases were of use primarily to interactive users and
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that they should normally not affect shell scripts called by those
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users; functions are available to such scripts.
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.LP
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Historical versions of the KornShell had not written aliases in a
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quoted manner suitable for reentry to the shell, but this
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volume of IEEE\ Std\ 1003.1-2001 has made this a requirement for all
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similar output. Therefore, consistency with this
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volume of IEEE\ Std\ 1003.1-2001 was chosen over this detail of historical
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practice.
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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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\fIFunction Definition Command\fP
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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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