1UNEXPAND(P) POSIX Programmer's Manual UNEXPAND(P)
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6 unexpand - convert spaces to tabs
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9 unexpand [ -a| -t tablist][file...]
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12 The unexpand utility shall copy files or standard input to standard
13 output, converting <blank>s at the beginning of each line into the max‐
14 imum number of <tab>s followed by the minimum number of <space>s needed
15 to fill the same column positions originally filled by the translated
16 <blank>s. By default, tabstops shall be set at every eighth column
17 position. Each <backspace> shall be copied to the output, and shall
18 cause the column position count for tab calculations to be decremented;
19 the count shall never be decremented to a value less than one.
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22 The unexpand utility shall conform to the Base Definitions volume of
23 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
24 The following options shall be supported:
26 -a In addition to translating <blank>s at the beginning of each
28 line, translate all sequences of two or more <blank>s immedi‐
29 ately preceding a tab stop to the maximum number of <tab>s fol‐
30 lowed by the minimum number of <space>s needed to fill the same
31 column positions originally filled by the translated <blank>s.
32 -t tablist
34 Specify the tab stops. The application shall ensure that the
35 tablist option-argument is a single argument consisting of a
36 single positive decimal integer or multiple positive decimal
37 integers, separated by <blank>s or commas, in ascending order.
38 If a single number is given, tabs shall be set tablist column
39 positions apart instead of the default 8. If multiple numbers
40 are given, the tabs shall be set at those specific column posi‐
41 tions.
42 The application shall ensure that each tab-stop position N is an inte‐
44 ger value greater than zero, and the list shall be in strictly ascend‐
45 ing order. This is taken to mean that, from the start of a line of out‐
46 put, tabbing to position N shall cause the next character output to be
47 in the ( N+1)th column position on that line. When the -t option is not
48 specified, the default shall be the equivalent of specifying -t 8
49 (except for the interaction with -a, described below).
50 No <space>-to- <tab> conversions shall occur for characters at posi‐
52 tions beyond the last of those specified in a multiple tab-stop list.
53 When -t is specified, the presence or absence of the -a option shall be
55 ignored; conversion shall not be limited to the processing of leading
56 <blank>s.
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60 The following operand shall be supported:
61 file A pathname of a text file to be used as input.
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66 See the INPUT FILES section.
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69 The input files shall be text files.
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72 The following environment variables shall affect the execution of unex‐
73 pand:
74 LANG Provide a default value for the internationalization variables
76 that are unset or null. (See the Base Definitions volume of
77 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
78 ables for the precedence of internationalization variables used
79 to determine the values of locale categories.)
80 LC_ALL If set to a non-empty string value, override the values of all
82 the other internationalization variables.
83 LC_CTYPE
85 Determine the locale for the interpretation of sequences of
86 bytes of text data as characters (for example, single-byte as
87 opposed to multi-byte characters in arguments and input files),
88 the processing of <tab>s and <space>s, and for the determination
89 of the width in column positions each character would occupy on
90 an output device.
91 LC_MESSAGES
93 Determine the locale that should be used to affect the format
94 and contents of diagnostic messages written to standard error.
95 NLSPATH
97 Determine the location of message catalogs for the processing of
98 LC_MESSAGES .
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102 Default.
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105 The standard output shall be equivalent to the input files with the
106 specified <space>-to- <tab> conversions.
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109 The standard error shall be used only for diagnostic messages.
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112 None.
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115 None.
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118 The following exit values shall be returned:
119 0 Successful completion.
121 >0 An error occurred.
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126 Default.
127 The following sections are informative.
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131 One non-intuitive aspect of unexpand is its restriction to leading spa‐
132 ces when neither -a nor -t is specified. Users who always want to con‐
133 vert all spaces in a file can easily alias unexpand to use the -a or
134 -t 8 option.
135
137 None.
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140 On several occasions, consideration was given to adding a -t option to
141 the unexpand utility to complement the -t in expand (see expand ). The
142 historical intent of unexpand was to translate multiple <blank>s into
143 tab stops, where tab stops were a multiple of eight column positions on
144 most UNIX systems. An early proposal omitted -t because it seemed out‐
145 side the scope of the User Portability Utilities option; it was not
146 described in any of the base documents. However, hard-coding tab stops
147 every eight columns was not suitable for the international community
148 and broke historical precedents for some vendors in the FORTRAN commu‐
149 nity, so -t was restored in conjunction with the list of valid exten‐
150 sion categories considered by the standard developers. Thus, unexpand
151 is now the logical converse of expand.
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154 None.
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157 expand , tabs
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160 Portions of this text are reprinted and reproduced in electronic form
161 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
162 -- Portable Operating System Interface (POSIX), The Open Group Base
163 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
164 Electrical and Electronics Engineers, Inc and The Open Group. In the
165 event of any discrepancy between this version and the original IEEE and
166 The Open Group Standard, the original IEEE and The Open Group Standard
167 is the referee document. The original Standard can be obtained online
168 at http://www.opengroup.org/unix/online.html .
169IEEE/The Open Group 2003 UNEXPAND(P)