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30 .\" $Id: tabs.1,v 1.35 2021/12/25 19:04:39 tom Exp $
56 \fB@TABS@\fP \- set tabs on a terminal
58 \fB@TABS@\fP [\fIoptions\fP]] \fI[tabstop-list]\fP
61 The \fB@TABS@\fP program clears and sets tab-stops on the terminal.
62 This uses the terminfo \fBclear_all_tabs\fP and \fBset_tab\fP capabilities.
63 If either is absent, \fB@TABS@\fP is unable to clear/set tab-stops.
64 The terminal should be configured to use hard tabs, e.g.,
69 Like \fB@CLEAR@\fP(1), \fB@TABS@\fP writes to the standard output.
70 You can redirect the standard output to a file (which prevents
71 \fB@TABS@\fP from actually changing the tabstops),
72 and later \fBcat\fP the file to the screen, setting tabstops at that point.
74 These are hardware tabs, which cannot be queried rapidly by applications
75 running in the terminal, if at all.
76 Curses and other full-screen applications may use hardware tabs
77 in optimizing their output to the terminal.
78 If the hardware tabstops differ from the information in the terminal
79 database, the result is unpredictable.
80 Before running curses programs,
81 you should either reset tab-stops to the standard interval
86 or use the \fB@RESET@\fP program,
87 since the normal initialization sequences do not ensure that tab-stops
93 Tell \fB@TABS@\fP which terminal type to use.
94 If this option is not given, \fB@TABS@\fP will use the \fB$TERM\fP
96 If that is not set, it will use the \fIansi+tabs\fP entry.
99 The debugging option shows a ruler line, followed by two data lines.
100 The first data line shows the expected tab-stops marked with asterisks.
101 The second data line shows the actual tab-stops, marked with asterisks.
104 This option tells \fB@TABS@\fP to check the options and run any debugging
105 option, but not to modify the terminal settings.
108 reports the version of ncurses which was used in this program, and exits.
110 The \fB@TABS@\fP program processes a single list of tab stops.
111 The last option to be processed which defines a list is the one that
112 determines the list to be processed.
114 Use a single number as an option,
115 e.g., \*(``\fB\-5\fP\*('' to set tabs at the given
116 interval (in this case 1, 6, 11, 16, 21, etc.).
117 Tabs are repeated up to the right margin of the screen.
119 Use \*(``\fB\-0\fP\*('' to clear all tabs.
121 Use \*(``\fB\-8\fP\*('' to set tabs to the standard interval.
123 An explicit list can be defined after the options
124 (this does not use a \*(``\-\*('').
125 The values in the list must be in increasing numeric order,
126 and greater than zero.
127 They are separated by a comma or a blank, for example,
134 Use a \*(``+\*('' to treat a number
135 as an increment relative to the previous value,
141 which is equivalent to the 1,6,11,16,21 example.
142 .SS Predefined Tab-Stops
143 POSIX defines several predefined lists of tab stops.
146 Assembler, IBM S/370, first format
151 Assembler, IBM S/370, second format
166 COBOL compact format extended
168 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
178 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
186 UNIVAC 1100 Assembler
190 A few terminals provide the capability for changing their left/right margins.
191 The @TABS@ program has an option to use this feature:
194 The effect depends on whether the terminal has the margin capabilities:
197 If the terminal provides the capability for setting the left margin,
198 @TABS@ uses this, and adjusts the available width for tab-stops.
200 If the terminal does not provide the margin capabilities,
201 @TABS@ imitates the effect, putting the tab stops at the appropriate
203 The terminal's left-margin is not modified.
206 If the \fImargin\fP parameter is omitted, the default is 10.
207 Use \fB+m0\fP to reset the left margin,
208 i.e., to the left edge of the terminal's display.
209 Before setting a left-margin,
210 @TABS@ resets the margin to reduce problems which might arise
211 on moving the cursor before the current left-margin.
213 When setting or resetting the left-margin,
214 @TABS@ may reset the right-margin.
217 \fIIEEE Std 1003.1/The Open Group Base Specifications Issue 7\fP (POSIX.1-2008)
218 describes a \fBtabs\fP utility.
221 This standard describes a \fB+m\fP option, to set a terminal's left-margin.
222 Very few of the entries in the terminal database provide the
223 \fBsmgl\fP (\fBset_left_margin\fP) or
224 \fBsmglp\fP (\fBset_left_margin_parm\fP)
225 capability needed to support the feature.
227 There is no counterpart in X/Open Curses Issue 7 for this utility,
228 unlike \fB@TPUT@\fP(1).
230 The \fB\-d\fP (debug) and \fB\-n\fP (no-op) options are extensions not provided
231 by other implementations.
233 A \fBtabs\fP utility appeared in PWB/Unix 1.0 (1977).
234 There was a reduced version of the \fBtabs\fP utility
235 in Unix 7th edition and in 3BSD (1979).
236 The latter supported a single \*(``\-n\*('' option
237 (to cause the first tab stop to be set on the left margin).
238 That option is not documented by POSIX.
240 The PWB/Unix \fBtabs\fP utility, which was included in System III (1980),
241 used built-in tables rather than the terminal database,
242 to support a half-dozen hardcopy terminal (printer) types.
243 It also had built-in logic to support the left-margin,
244 as well as a feature for copying the tab settings from a file.
246 Later versions of Unix, e.g., SVr4,
247 added support for the terminal database,
248 but kept the tables to support the printers.
249 In an earlier development effort,
250 the tab-stop initialization provided by \fBtset\fP (1982)
251 and incorporated into \fBtput\fP uses the terminal database,
253 The \fB+m\fP option was documented
254 in the Base Specifications Issue 5 (Unix98, 1997),
255 and omitted in Issue 6 (Unix03, 2004) without documenting the rationale,
256 though an introductory comment
257 \fI\*(``and optionally adjusts the margin\*(''\fP remains,
258 overlooked in the removal.
259 The documented \fBtabs\fP utility in Issues 6 and later has no mechanism
261 The \fB+m\fP option in this implementation differs from the feature
262 in SVr4 by using terminal capabilities rather than built-in tables.
264 POSIX documents no limits on the number of tab stops.
265 Documentation for other implementations states that there is a limit on the
267 (e.g., 20 in PWB/Unix's \fBtabs\fP utility).
268 While some terminals may not accept an arbitrary number
269 of tab stops, this implementation will attempt to set tab stops up to the
270 right margin of the screen, if the given list happens to be that long.
272 The \fIRationale\fP section of the POSIX documentation goes into some
273 detail about the ways the committee considered redesigning the
274 \fBtabs\fP and \fBtput\fP utilities,
275 without proposing an improved solution.
279 no known historical version of tabs supports the capability of setting
283 However, the \fIExplicit Lists\fP described in this manual page
284 were implemented in PWB/Unix.
285 Those provide the capability of setting abitrary tab stops.
292 This describes \fBncurses\fP
293 version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch @NCURSES_PATCH@).