1UNEXPAND(1P) POSIX Programmer's Manual UNEXPAND(1P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 unexpand - convert spaces to tabs
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15 unexpand [ -a| -t tablist][file...]
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18 The unexpand utility shall copy files or standard input to standard
19 output, converting <blank>s at the beginning of each line into the max‐
20 imum number of <tab>s followed by the minimum number of <space>s needed
21 to fill the same column positions originally filled by the translated
22 <blank>s. By default, tabstops shall be set at every eighth column
23 position. Each <backspace> shall be copied to the output, and shall
24 cause the column position count for tab calculations to be decremented;
25 the count shall never be decremented to a value less than one.
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28 The unexpand utility shall conform to the Base Definitions volume of
29 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
30 The following options shall be supported:
32 -a In addition to translating <blank>s at the beginning of each
34 line, translate all sequences of two or more <blank>s immedi‐
35 ately preceding a tab stop to the maximum number of <tab>s fol‐
36 lowed by the minimum number of <space>s needed to fill the same
37 column positions originally filled by the translated <blank>s.
38 -t tablist
40 Specify the tab stops. The application shall ensure that the
41 tablist option-argument is a single argument consisting of a
42 single positive decimal integer or multiple positive decimal
43 integers, separated by <blank>s or commas, in ascending order.
44 If a single number is given, tabs shall be set tablist column
45 positions apart instead of the default 8. If multiple numbers
46 are given, the tabs shall be set at those specific column posi‐
47 tions.
48 The application shall ensure that each tab-stop position N is an inte‐
50 ger value greater than zero, and the list shall be in strictly ascend‐
51 ing order. This is taken to mean that, from the start of a line of out‐
52 put, tabbing to position N shall cause the next character output to be
53 in the ( N+1)th column position on that line. When the -t option is not
54 specified, the default shall be the equivalent of specifying -t 8
55 (except for the interaction with -a, described below).
56 No <space>-to- <tab> conversions shall occur for characters at posi‐
58 tions beyond the last of those specified in a multiple tab-stop list.
59 When -t is specified, the presence or absence of the -a option shall be
61 ignored; conversion shall not be limited to the processing of leading
62 <blank>s.
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66 The following operand shall be supported:
67 file A pathname of a text file to be used as input.
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72 See the INPUT FILES section.
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75 The input files shall be text files.
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78 The following environment variables shall affect the execution of unex‐
79 pand:
80 LANG Provide a default value for the internationalization variables
82 that are unset or null. (See the Base Definitions volume of
83 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
84 ables for the precedence of internationalization variables used
85 to determine the values of locale categories.)
86 LC_ALL If set to a non-empty string value, override the values of all
88 the other internationalization variables.
89 LC_CTYPE
91 Determine the locale for the interpretation of sequences of
92 bytes of text data as characters (for example, single-byte as
93 opposed to multi-byte characters in arguments and input files),
94 the processing of <tab>s and <space>s, and for the determination
95 of the width in column positions each character would occupy on
96 an output device.
97 LC_MESSAGES
99 Determine the locale that should be used to affect the format
100 and contents of diagnostic messages written to standard error.
101 NLSPATH
103 Determine the location of message catalogs for the processing of
104 LC_MESSAGES .
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108 Default.
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111 The standard output shall be equivalent to the input files with the
112 specified <space>-to- <tab> conversions.
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115 The standard error shall be used only for diagnostic messages.
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118 None.
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121 None.
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124 The following exit values shall be returned:
125 0 Successful completion.
127 >0 An error occurred.
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132 Default.
133 The following sections are informative.
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137 One non-intuitive aspect of unexpand is its restriction to leading spa‐
138 ces when neither -a nor -t is specified. Users who always want to con‐
139 vert all spaces in a file can easily alias unexpand to use the -a or
140 -t 8 option.
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143 None.
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146 On several occasions, consideration was given to adding a -t option to
147 the unexpand utility to complement the -t in expand (see expand ). The
148 historical intent of unexpand was to translate multiple <blank>s into
149 tab stops, where tab stops were a multiple of eight column positions on
150 most UNIX systems. An early proposal omitted -t because it seemed out‐
151 side the scope of the User Portability Utilities option; it was not
152 described in any of the base documents. However, hard-coding tab stops
153 every eight columns was not suitable for the international community
154 and broke historical precedents for some vendors in the FORTRAN commu‐
155 nity, so -t was restored in conjunction with the list of valid exten‐
156 sion categories considered by the standard developers. Thus, unexpand
157 is now the logical converse of expand.
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160 None.
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163 expand, tabs
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166 Portions of this text are reprinted and reproduced in electronic form
167 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
168 -- Portable Operating System Interface (POSIX), The Open Group Base
169 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
170 Electrical and Electronics Engineers, Inc and The Open Group. In the
171 event of any discrepancy between this version and the original IEEE and
172 The Open Group Standard, the original IEEE and The Open Group Standard
173 is the referee document. The original Standard can be obtained online
174 at http://www.opengroup.org/unix/online.html .
175IEEE/The Open Group 2003 UNEXPAND(1P)