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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13 unexpand — convert spaces to tabs
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16 unexpand [−a|−t tablist] [file...]
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19 The unexpand utility shall copy files or standard input to standard
20 output, converting <blank> characters at the beginning of each line
21 into the maximum number of <tab> characters followed by the minimum
22 number of <space> characters needed to fill the same column positions
23 originally filled by the translated <blank> characters. By default,
24 tabstops shall be set at every eighth column position. Each <backspace>
25 shall be copied to the output, and shall cause the column position
26 count for tab calculations to be decremented; the count shall never be
27 decremented to a value less than one.
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30 The unexpand utility shall conform to the Base Definitions volume of
31 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
32 The following options shall be supported:
34 −a In addition to translating <blank> characters at the begin‐
36 ning of each line, translate all sequences of two or more
37 <blank> characters immediately preceding a tab stop to the
38 maximum number of <tab> characters followed by the minimum
39 number of <space> characters needed to fill the same column
40 positions originally filled by the translated <blank> charac‐
41 ters.
42 −t tablist
44 Specify the tab stops. The application shall ensure that the
45 tablist option-argument is a single argument consisting of a
46 single positive decimal integer or multiple positive decimal
47 integers, separated by <blank> or <comma> characters, in
48 ascending order. If a single number is given, tabs shall be
49 set tablist column positions apart instead of the default 8.
50 If multiple numbers are given, the tabs shall be set at those
51 specific column positions.
52 The application shall ensure that each tab-stop position N is
54 an integer value greater than zero, and the list shall be in
55 strictly ascending order. This is taken to mean that, from
56 the start of a line of output, tabbing to position N shall
57 cause the next character output to be in the (N+1)th column
58 position on that line. When the −t option is not specified,
59 the default shall be the equivalent of specifying −t 8
60 (except for the interaction with −a, described below).
61 No <space>-to-<tab> conversions shall occur for characters at
63 positions beyond the last of those specified in a multiple
64 tab-stop list.
65 When −t is specified, the presence or absence of the −a
67 option shall be ignored; conversion shall not be limited to
68 the processing of leading <blank> characters.
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71 The following operand shall be supported:
72 file A pathname of a text file to be used as input.
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76 See the INPUT FILES section.
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79 The input files shall be text files.
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82 The following environment variables shall affect the execution of unex‐
83 pand:
84 LANG Provide a default value for the internationalization vari‐
86 ables that are unset or null. (See the Base Definitions vol‐
87 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
88 ables for the precedence of internationalization variables
89 used to determine the values of locale categories.)
90 LC_ALL If set to a non-empty string value, override the values of
92 all the other internationalization variables.
93 LC_CTYPE Determine the locale for the interpretation of sequences of
95 bytes of text data as characters (for example, single-byte as
96 opposed to multi-byte characters in arguments and input
97 files), the processing of <tab> and <space> characters, and
98 for the determination of the width in column positions each
99 character would occupy on an output device.
100 LC_MESSAGES
102 Determine the locale that should be used to affect the format
103 and contents of diagnostic messages written to standard
104 error.
105 NLSPATH Determine the location of message catalogs for the processing
107 of LC_MESSAGES.
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110 Default.
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113 The standard output shall be equivalent to the input files with the
114 specified <space>-to-<tab> conversions.
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117 The standard error shall be used only for diagnostic messages.
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120 None.
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123 None.
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126 The following exit values shall be returned:
127 0 Successful completion.
129 >0 An error occurred.
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133 Default.
134 The following sections are informative.
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138 One non-intuitive aspect of unexpand is its restriction to leading
139 <space> characters when neither −a nor −t is specified. Users who
140 always want to convert all <space> characters in a file can easily
141 alias unexpand to use the −a or −t 8 option.
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144 None.
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147 On several occasions, consideration was given to adding a −t option to
148 the unexpand utility to complement the −t in expand (see expand). The
149 historical intent of unexpand was to translate multiple <blank> charac‐
150 ters into tab stops, where tab stops were a multiple of eight column
151 positions on most UNIX systems. An early proposal omitted −t because it
152 seemed outside the scope of the User Portability Utilities option; it
153 was not described in any of the base documents. However, hard-coding
154 tab stops every eight columns was not suitable for the international
155 community and broke historical precedents for some vendors in the FOR‐
156 TRAN community, so −t was restored in conjunction with the list of
157 valid extension categories considered by the standard developers. Thus,
158 unexpand is now the logical converse of expand.
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161 None.
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164 expand, tabs
165 The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
167 Variables, Section 12.2, Utility Syntax Guidelines
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170 Portions of this text are reprinted and reproduced in electronic form
171 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
172 -- Portable Operating System Interface (POSIX), The Open Group Base
173 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
174 cal and Electronics Engineers, Inc and The Open Group. (This is
175 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
176 event of any discrepancy between this version and the original IEEE and
177 The Open Group Standard, the original IEEE and The Open Group Standard
178 is the referee document. The original Standard can be obtained online
179 at http://www.unix.org/online.html .
180 Any typographical or formatting errors that appear in this page are
182 most likely to have been introduced during the conversion of the source
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184 nel.org/doc/man-pages/reporting_bugs.html .
185IEEE/The Open Group 2013 UNEXPAND(1P)