1TABS(1P) POSIX Programmer's Manual TABS(1P)
2
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.
10
12 tabs — set terminal tabs
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15 tabs [-n|-a|-a2|-c|-c2|-c3|-f|-p|-s|-u] [-T type]
16 tabs [-T type] n[[sep[+]n]...]
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20 The tabs utility shall display a series of characters that first clears
21 the hardware terminal tab settings and then initializes the tab stops
22 at the specified positions and optionally adjusts the margin.
23 The phrase ``tab-stop position N'' shall be taken to mean that, from
25 the start of a line of output, tabbing to position N shall cause the
26 next character output to be in the (N+1)th column position on that
27 line. The maximum number of tab stops allowed is terminal-dependent.
28 It need not be possible to implement tabs on certain terminals. If the
30 terminal type obtained from the TERM environment variable or -T option
31 represents such a terminal, an appropriate diagnostic message shall be
32 written to standard error and tabs shall exit with a status greater
33 than zero.
34
36 The tabs utility shall conform to the Base Definitions volume of
37 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines, except for vari‐
38 ous extensions: the options -a2, -c2, and -c3 are multi-character.
39 The following options shall be supported:
41 -n Specify repetitive tab stops separated by a uniform number of
43 column positions, n, where n is a single-digit decimal num‐
44 ber. The default usage of tabs with no arguments shall be
45 equivalent to tabs -8. When -0 is used, the tab stops shall
46 be cleared and no new ones set.
47 -a 1,10,16,36,72
49 Assembler, applicable to some mainframes.
50 -a2 1,10,16,40,72
52 Assembler, applicable to some mainframes.
53 -c 1,8,12,16,20,55
55 COBOL, normal format.
56 -c2 1,6,10,14,49
58 COBOL, compact format (columns 1 to 6 omitted).
59 -c3 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
61 COBOL compact format (columns 1 to 6 omitted), with more tabs
62 than -c2.
63 -f 1,7,11,15,19,23
65 FORTRAN
66 -p 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
68 PL/1
69 -s 1,10,55
71 SNOBOL
72 -u 1,12,20,44
74 Assembler, applicable to some mainframes.
75 -T type Indicate the type of terminal. If this option is not supplied
77 and the TERM variable is unset or null, an unspecified
78 default terminal type shall be used. The setting of type
79 shall take precedence over the value in TERM.
80
82 The following operand shall be supported:
83 n[[sep[+]n]...]
85 A single command line argument that consists of one or more
86 tab-stop values (n) separated by a separator character (sep)
87 which is either a <comma> or a <blank> character. The appli‐
88 cation shall ensure that the tab-stop values are positive
89 decimal integers in strictly ascending order. If any tab-stop
90 value (except the first one) is preceded by a <plus-sign>, it
91 is taken as an increment to be added to the previous value.
92 For example, the tab lists 1,10,20,30 and "110+10+10" are
93 considered to be identical.
94
96 Not used.
97
99 None.
100
102 The following environment variables shall affect the execution of tabs:
103 LANG Provide a default value for the internationalization vari‐
105 ables that are unset or null. (See the Base Definitions vol‐
106 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
107 ables for the precedence of internationalization variables
108 used to determine the values of locale categories.)
109 LC_ALL If set to a non-empty string value, override the values of
111 all the other internationalization variables.
112 LC_CTYPE Determine the locale for the interpretation of sequences of
114 bytes of text data as characters (for example, single-byte as
115 opposed to multi-byte characters in arguments).
116 LC_MESSAGES
118 Determine the locale that should be used to affect the format
119 and contents of diagnostic messages written to standard
120 error.
121 NLSPATH Determine the location of message catalogs for the processing
123 of LC_MESSAGES.
124 TERM Determine the terminal type. If this variable is unset or
126 null, and if the -T option is not specified, an unspecified
127 default terminal type shall be used.
128
130 Default.
131
133 If standard output is a terminal, the appropriate sequence to clear and
134 set the tab stops may be written to standard output in an unspecified
135 format. If standard output is not a terminal, undefined results occur.
136
138 The standard error shall be used only for diagnostic messages.
139
141 None.
142
144 None.
145
147 The following exit values shall be returned:
148 0 Successful completion.
150 >0 An error occurred.
152
154 Default.
155 The following sections are informative.
157
159 This utility makes use of the terminal's hardware tabs and the stty
160 tabs option.
161 This utility is not recommended for application use.
163 Some integrated display units might not have escape sequences to set
165 tab stops, but may be set by internal system calls. On these terminals,
166 tabs works if standard output is directed to the terminal; if output is
167 directed to another file, however, tabs fails.
168
170 None.
171
173 Consideration was given to having the tput utility handle all of the
174 functions described in tabs. However, the separate tabs utility was
175 retained because it seems more intuitive to use a command named tabs
176 than tput with a new option. The tput utility does not support setting
177 or clearing tabs, and no known historical version of tabs supports the
178 capability of setting arbitrary tab stops.
179 The System V tabs interface is very complex; the version in this volume
181 of POSIX.1‐2017 has a reduced feature list, but many of the features
182 omitted were restored as part of the XSI option even though the sup‐
183 ported languages and coding styles are primarily historical.
184 There was considerable sentiment for specifying only a means of reset‐
186 ting the tabs back to a known state—presumably the ``standard'' of tabs
187 every eight positions. The following features were omitted:
188 * Setting tab stops via the first line in a file, using --file.
190 Since even the SVID has no complete explanation of this feature, it
191 is doubtful that it is in widespread use.
192 In an early proposal, a -t tablist option was added for consistency
194 with expand; this was later removed when inconsistencies with the his‐
195 torical list of tabs were identified.
196 Consideration was given to adding a -p option that would output the
198 current tab settings so that they could be saved and then later
199 restored. This was not accepted because querying the tab stops of the
200 terminal is not a capability in historical terminfo or termcap facili‐
201 ties and might not be supported on a wide range of terminals.
202
204 None.
205
207 expand, stty, tput, unexpand
208 The Base Definitions volume of POSIX.1‐2017, Chapter 8, Environment
210 Variables, Section 12.2, Utility Syntax Guidelines
211
213 Portions of this text are reprinted and reproduced in electronic form
214 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
215 table Operating System Interface (POSIX), The Open Group Base Specifi‐
216 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
217 Electrical and Electronics Engineers, Inc and The Open Group. In the
218 event of any discrepancy between this version and the original IEEE and
219 The Open Group Standard, the original IEEE and The Open Group Standard
220 is the referee document. The original Standard can be obtained online
221 at http://www.opengroup.org/unix/online.html .
222 Any typographical or formatting errors that appear in this page are
224 most likely to have been introduced during the conversion of the source
225 files to man page format. To report such errors, see https://www.ker‐
226 nel.org/doc/man-pages/reporting_bugs.html .
227IEEE/The Open Group 2017 TABS(1P)