1tabs(1)                     General Commands Manual                    tabs(1)
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NAME

6       tabs - set tabs on a terminal
7

SYNOPSIS

9       tabs [options]] [tabstop-list]
10

DESCRIPTION

12       The  tabs program clears and sets tab-stops on the terminal.  This uses
13       the terminfo clear_all_tabs and set_tab capabilities.  If either is ab‐
14       sent,  tabs  is  unable to clear/set tab-stops.  The terminal should be
15       configured to use hard tabs, e.g.,
16
17           stty tab0
18
19       Like clear(1), tabs writes to the standard output.   You  can  redirect
20       the standard output to a file (which prevents tabs from actually chang‐
21       ing the tabstops), and later cat the file to the screen,  setting  tab‐
22       stops at that point.
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24       These  are  hardware  tabs, which cannot be queried rapidly by applica‐
25       tions running in the terminal, if at all.  Curses and other full-screen
26       applications  may  use  hardware tabs in optimizing their output to the
27       terminal.  If the hardware tabstops differ from the information in  the
28       terminal  database, the result is unpredictable.  Before running curses
29       programs, you should either reset tab-stops to the standard interval
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31           tabs -8
32
33       or use the reset program, since the normal initialization sequences  do
34       not ensure that tab-stops are reset.
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OPTIONS

37   General Options
38       -Tname
39            Tell  tabs  which  terminal  type  to  use.  If this option is not
40            given, tabs will use the $TERM environment variable.  If  that  is
41            not set, it will use the ansi+tabs entry.
42
43       -d   The  debugging  option  shows  a  ruler line, followed by two data
44            lines.  The first data line shows the  expected  tab-stops  marked
45            with  asterisks.  The second data line shows the actual tab-stops,
46            marked with asterisks.
47
48       -n   This option tells tabs to check the options and run any  debugging
49            option, but not to modify the terminal settings.
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51       -V   reports the version of ncurses which was used in this program, and
52            exits.
53
54       The tabs program processes a single list of tab stops.  The last option
55       to  be  processed  which  defines a list is the one that determines the
56       list to be processed.
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58   Implicit Lists
59       Use a single number as an option, e.g., “-5” to set tabs at  the  given
60       interval  (in  this case 1, 6, 11, 16, 21, etc.).  Tabs are repeated up
61       to the right margin of the screen.
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63       Use “-0” to clear all tabs.
64
65       Use “-8” to set tabs to the standard interval.
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67   Explicit Lists
68       An explicit list can be defined after the options (this does not use  a
69       “-”).   The values in the list must be in increasing numeric order, and
70       greater than zero.  They are separated by a comma or a blank, for exam‐
71       ple,
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73           tabs 1,6,11,16,21
74           tabs 1 6 11 16 21
75
76       Use  a  “+”  to treat a number as an increment relative to the previous
77       value, e.g.,
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79           tabs 1,+5,+5,+5,+5
80
81       which is equivalent to the 1,6,11,16,21 example.
82
83   Predefined Tab-Stops
84       X/Open defines several predefined lists of tab stops.
85
86       -a   Assembler, IBM S/370, first format
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88       -a2  Assembler, IBM S/370, second format
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90       -c   COBOL, normal format
91
92       -c2  COBOL compact format
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94       -c3  COBOL compact format extended
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96       -f   FORTRAN
97
98       -p   PL/I
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100       -s   SNOBOL
101
102       -u   UNIVAC 1100 Assembler
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PORTABILITY

105       IEEE  Std  1003.1/The  Open   Group   Base   Specifications   Issue   7
106       (POSIX.1-2008) describes a tabs utility.  However
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108       •   This  standard describes a +m option, to set a terminal's left-mar‐
109           gin.  Very few of the entries in the terminal database provide  the
110           smgl  (set_left_margin)  or smglp (set_left_margin_parm) capability
111           needed to support the feature.
112
113       •   There is no counterpart in X/Open Curses Issue 7 for this  utility,
114           unlike tput(1).
115
116       The  -d  (debug)  and -n (no-op) options are extensions not provided by
117       other implementations.
118
119       A tabs utility appeared in PWB/Unix 1.0 (1977).  There  was  a  reduced
120       version  of  the  tabs  utility in Unix 7th edition and in 3BSD (1979).
121       The latter supported a single “-n” option (to cause the first tab  stop
122       to be set on the left margin).  That option is not documented by POSIX.
123
124       The  PWB/Unix  tabs  utility,  which was included in System III (1980),
125       used built-in tables rather than the terminal database,  to  support  a
126       half-dozen  terminal  types.  It also had built-in logic to support the
127       left-margin, as well as a feature for copying the tab settings  from  a
128       file.
129
130       Later  versions  of  Unix,  e.g.,  SVr4, added support for the terminal
131       database, but kept the tables, as a fallback.  In an  earlier  develop‐
132       ment  effort,  the  tab-stop initialization provided by tset (1982) and
133       incorporated into tput uses the terminal database,
134
135       POSIX documents no limits on the number of  tab  stops.   Documentation
136       for other implementations states that there is a limit on the number of
137       tab stops (e.g., 20 in PWB/Unix's tabs utility).  While some  terminals
138       may  not  accept  an arbitrary number of tab stops, this implementation
139       will attempt to set tab stops up to the right margin of the screen,  if
140       the given list happens to be that long.
141
142       The  Rationale section of the POSIX documentation goes into some detail
143       about the ways the committee considered redesigning the tabs  and  tput
144       utilities, without proposing an improved solution.  It comments that
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146            no  known  historical  version  of tabs supports the capability of
147            setting arbitrary tab stops.
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149       However, the Explicit Lists described in this manual page  were  imple‐
150       mented  in  PWB/Unix.  Those provide the capability of setting abitrary
151       tab stops.
152

SEE ALSO

154       infocmp(1M), tset(1), curses(3X), terminfo(5).
155
156       This describes ncurses version 6.2 (patch 20210508).
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160                                                                       tabs(1)
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