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
13 tabs — set terminal tabs
14
16 tabs [−n|−a|−a2|−c|−c2|−c3|−f|−p|−s|−u] [−T type]
17 tabs [−T type] n[[sep[+]n]...]
19
21 The tabs utility shall display a series of characters that first clears
22 the hardware terminal tab settings and then initializes the tab stops
23 at the specified positions and optionally adjusts the margin.
24 The phrase ``tab-stop position N'' shall be taken to mean that, from
26 the start of a line of output, tabbing to position N shall cause the
27 next character output to be in the (N+1)th column position on that
28 line. The maximum number of tab stops allowed is terminal-dependent.
29 It need not be possible to implement tabs on certain terminals. If the
31 terminal type obtained from the TERM environment variable or −T option
32 represents such a terminal, an appropriate diagnostic message shall be
33 written to standard error and tabs shall exit with a status greater
34 than zero.
35
37 The tabs utility shall conform to the Base Definitions volume of
38 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except for vari‐
39 ous extensions: the options −a2, −c2, and −c3 are multi-character.
40 The following options shall be supported:
42 −n Specify repetitive tab stops separated by a uniform number of
44 column positions, n, where n is a single-digit decimal num‐
45 ber. The default usage of tabs with no arguments shall be
46 equivalent to tabs −8. When −0 is used, the tab stops shall
47 be cleared and no new ones set.
48 −a 1,10,16,36,72
50 Assembler, applicable to some mainframes.
51 −a2 1,10,16,40,72
53 Assembler, applicable to some mainframes.
54 −c 1,8,12,16,20,55
56 COBOL, normal format.
57 −c2 1,6,10,14,49
59 COBOL, compact format (columns 1 to 6 omitted).
60 −c3 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
62 COBOL compact format (columns 1 to 6 omitted), with more tabs
63 than −c2.
64 −f 1,7,11,15,19,23
66 FORTRAN
67 −p 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
69 PL/1
70 −s 1,10,55
72 SNOBOL
73 −u 1,12,20,44
75 Assembler, applicable to some mainframes.
76 −T type Indicate the type of terminal. If this option is not supplied
78 and the TERM variable is unset or null, an unspecified
79 default terminal type shall be used. The setting of type
80 shall take precedence over the value in TERM.
81
83 The following operand shall be supported:
84 n[[sep[+]n]...]
86 A single command line argument that consists of one or more
87 tab-stop values (n) separated by a separator character (sep)
88 which is either a <comma> or a <blank> character. The appli‐
89 cation shall ensure that the tab-stop values are positive
90 decimal integers in strictly ascending order. If any tab-stop
91 value (except the first one) is preceded by a <plus-sign>, it
92 is taken as an increment to be added to the previous value.
93 For example, the tab lists 1,10,20,30 and "110+10+10" are
94 considered to be identical.
95
97 Not used.
98
100 None.
101
103 The following environment variables shall affect the execution of tabs:
104 LANG Provide a default value for the internationalization vari‐
106 ables that are unset or null. (See the Base Definitions vol‐
107 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
108 ables for the precedence of internationalization variables
109 used to determine the values of locale categories.)
110 LC_ALL If set to a non-empty string value, override the values of
112 all the other internationalization variables.
113 LC_CTYPE Determine the locale for the interpretation of sequences of
115 bytes of text data as characters (for example, single-byte as
116 opposed to multi-byte characters in arguments).
117 LC_MESSAGES
119 Determine the locale that should be used to affect the format
120 and contents of diagnostic messages written to standard
121 error.
122 NLSPATH Determine the location of message catalogs for the processing
124 of LC_MESSAGES.
125 TERM Determine the terminal type. If this variable is unset or
127 null, and if the −T option is not specified, an unspecified
128 default terminal type shall be used.
129
131 Default.
132
134 If standard output is a terminal, the appropriate sequence to clear and
135 set the tab stops may be written to standard output in an unspecified
136 format. If standard output is not a terminal, undefined results occur.
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139 The standard error shall be used only for diagnostic messages.
140
142 None.
143
145 None.
146
148 The following exit values shall be returned:
149 0 Successful completion.
151 >0 An error occurred.
153
155 Default.
156 The following sections are informative.
158
160 This utility makes use of the terminal's hardware tabs and the stty
161 tabs option.
162 This utility is not recommended for application use.
164 Some integrated display units might not have escape sequences to set
166 tab stops, but may be set by internal system calls. On these terminals,
167 tabs works if standard output is directed to the terminal; if output is
168 directed to another file, however, tabs fails.
169
171 None.
172
174 Consideration was given to having the tput utility handle all of the
175 functions described in tabs. However, the separate tabs utility was
176 retained because it seems more intuitive to use a command named tabs
177 than tput with a new option. The tput utility does not support setting
178 or clearing tabs, and no known historical version of tabs supports the
179 capability of setting arbitrary tab stops.
180 The System V tabs interface is very complex; the version in this volume
182 of POSIX.1‐2008 has a reduced feature list, but many of the features
183 omitted were restored as part of the XSI option even though the sup‐
184 ported languages and coding styles are primarily historical.
185 There was considerable sentiment for specifying only a means of reset‐
187 ting the tabs back to a known state—presumably the ``standard'' of tabs
188 every eight positions. The following features were omitted:
189 * Setting tab stops via the first line in a file, using −−file.
191 Since even the SVID has no complete explanation of this feature, it
192 is doubtful that it is in widespread use.
193 In an early proposal, a −t tablist option was added for consistency
195 with expand; this was later removed when inconsistencies with the his‐
196 torical list of tabs were identified.
197 Consideration was given to adding a −p option that would output the
199 current tab settings so that they could be saved and then later
200 restored. This was not accepted because querying the tab stops of the
201 terminal is not a capability in historical terminfo or termcap facili‐
202 ties and might not be supported on a wide range of terminals.
203
205 None.
206
208 expand, stty, tput, unexpand
209 The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
211 Variables, Section 12.2, Utility Syntax Guidelines
212
214 Portions of this text are reprinted and reproduced in electronic form
215 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
216 -- Portable Operating System Interface (POSIX), The Open Group Base
217 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
218 cal and Electronics Engineers, Inc and The Open Group. (This is
219 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
220 event of any discrepancy between this version and the original IEEE and
221 The Open Group Standard, the original IEEE and The Open Group Standard
222 is the referee document. The original Standard can be obtained online
223 at http://www.unix.org/online.html .
224 Any typographical or formatting errors that appear in this page are
226 most likely to have been introduced during the conversion of the source
227 files to man page format. To report such errors, see https://www.ker‐
228 nel.org/doc/man-pages/reporting_bugs.html .
229IEEE/The Open Group 2013 TABS(1P)