mirror of https://github.com/mkerrisk/man-pages
183 lines
6.4 KiB
Groff
183 lines
6.4 KiB
Groff
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "UNEXPAND" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" unexpand
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.SH NAME
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unexpand \- convert spaces to tabs
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.SH SYNOPSIS
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.LP
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\fBunexpand\fP \fB[\fP \fB-a| -t\fP \fItablist\fP\fB][\fP\fIfile\fP\fB...\fP\fB]\fP\fB\fP
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.SH DESCRIPTION
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.LP
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The \fIunexpand\fP utility shall copy files or standard input to standard
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output, converting <blank>s at the beginning of
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each line into the maximum number of <tab>s followed by the minimum
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number of <space>s needed to fill the same column
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positions originally filled by the translated <blank>s. By default,
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tabstops shall be set at every eighth column position.
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Each <backspace> shall be copied to the output, and shall cause the
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column position count for tab calculations to be
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decremented; the count shall never be decremented to a value less
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than one.
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.SH OPTIONS
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.LP
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The \fIunexpand\fP utility shall conform to the Base Definitions volume
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of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
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.LP
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The following options shall be supported:
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.TP 7
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\fB-a\fP
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In addition to translating <blank>s at the beginning of each line,
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translate all sequences of two or more <blank>s
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immediately preceding a tab stop to the maximum number of <tab>s followed
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by the minimum number of <space>s needed to
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fill the same column positions originally filled by the translated
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<blank>s.
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.TP 7
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\fB-t\ \fP \fItablist\fP
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Specify the tab stops. The application shall ensure that the \fItablist\fP
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option-argument is a single argument consisting of
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a single positive decimal integer or multiple positive decimal integers,
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separated by <blank>s or commas, in ascending order.
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If a single number is given, tabs shall be set \fItablist\fP column
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positions apart instead of the default 8. If multiple numbers
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are given, the tabs shall be set at those specific column positions.
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.LP
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The application shall ensure that each tab-stop position \fIN\fP is
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an integer value greater than zero, and the list shall be
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in strictly ascending order. This is taken to mean that, from the
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start of a line of output, tabbing to position \fIN\fP shall
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cause the next character output to be in the ( \fIN\fP+1)th column
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position on that line. When the \fB-t\fP option is not
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specified, the default shall be the equivalent of specifying \fB-t\ 8\fP
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(except for the interaction with \fB-a\fP, described
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below).
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.LP
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No <space>-to- <tab> conversions shall occur for characters at positions
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beyond the last of those specified in a
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multiple tab-stop list.
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.LP
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When \fB-t\fP is specified, the presence or absence of the \fB-a\fP
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option shall be ignored; conversion shall not be limited
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to the processing of leading <blank>s.
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.sp
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.SH OPERANDS
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.LP
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The following operand shall be supported:
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.TP 7
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\fIfile\fP
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A pathname of a text file to be used as input.
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.sp
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.SH STDIN
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.LP
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See the INPUT FILES section.
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.SH INPUT FILES
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.LP
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The input files shall be text files.
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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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\fIunexpand\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), the
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processing of <tab>s and <space>s, and for the
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determination of the width in column positions each character would
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occupy on an output device.
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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 standard output shall be equivalent to the input files with the
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specified <space>-to- <tab> conversions.
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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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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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One non-intuitive aspect of \fIunexpand\fP is its restriction to leading
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spaces when neither \fB-a\fP nor \fB-t\fP is
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specified. Users who always want to convert all spaces in a file can
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easily alias \fIunexpand\fP to use the \fB-a\fP or
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\fB-t\ 8\fP option.
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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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On several occasions, consideration was given to adding a \fB-t\fP
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option to the \fIunexpand\fP utility to complement the
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\fB-t\fP in \fIexpand\fP (see \fIexpand\fP ). The historical
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intent of \fIunexpand\fP was to translate multiple <blank>s into tab
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stops, where tab stops were a multiple of eight column
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positions on most UNIX systems. An early proposal omitted \fB-t\fP
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because it seemed outside the scope of the User Portability
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Utilities option; it was not described in any of the base documents.
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However, hard-coding tab stops every eight columns was not
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suitable for the international community and broke historical precedents
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for some vendors in the FORTRAN community, so \fB-t\fP
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was restored in conjunction with the list of valid extension categories
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considered by the standard developers. Thus,
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\fIunexpand\fP is now the logical converse of \fIexpand\fP.
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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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\fIexpand\fP , \fItabs\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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