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30 * @Id: tabs.1,v 1.35 2021/12/25 19:04:39 tom Exp @
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42 <H1 class="no-header">tabs 1</H1>
44 <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG> General Commands Manual <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
49 </PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
50 <STRONG>tabs</STRONG> - set tabs on a terminal
53 </PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
54 <STRONG>tabs</STRONG> [<EM>options</EM>]] <EM>[tabstop-list]</EM>
57 </PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
58 The <STRONG>tabs</STRONG> program clears and sets tab-stops on the terminal. This uses
59 the terminfo <STRONG>clear_all_tabs</STRONG> and <STRONG>set_tab</STRONG> capabilities. If either is
60 absent, <STRONG>tabs</STRONG> is unable to clear/set tab-stops. The terminal should be
61 configured to use hard tabs, e.g.,
65 Like <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>, <STRONG>tabs</STRONG> writes to the standard output. You can redirect
66 the standard output to a file (which prevents <STRONG>tabs</STRONG> from actually
67 changing the tabstops), and later <STRONG>cat</STRONG> the file to the screen, setting
68 tabstops at that point.
70 These are hardware tabs, which cannot be queried rapidly by
71 applications running in the terminal, if at all. Curses and other
72 full-screen applications may use hardware tabs in optimizing their
73 output to the terminal. If the hardware tabstops differ from the
74 information in the terminal database, the result is unpredictable.
75 Before running curses programs, you should either reset tab-stops to
80 or use the <STRONG>reset</STRONG> program, since the normal initialization sequences do
81 not ensure that tab-stops are reset.
84 </PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
86 </PRE><H3><a name="h3-General-Options">General Options</a></H3><PRE>
87 <STRONG>-T</STRONG><EM>name</EM>
88 Tell <STRONG>tabs</STRONG> which terminal type to use. If this option is not
89 given, <STRONG>tabs</STRONG> will use the <STRONG>$TERM</STRONG> environment variable. If that is
90 not set, it will use the <EM>ansi+tabs</EM> entry.
92 <STRONG>-d</STRONG> The debugging option shows a ruler line, followed by two data
93 lines. The first data line shows the expected tab-stops marked
94 with asterisks. The second data line shows the actual tab-stops,
95 marked with asterisks.
97 <STRONG>-n</STRONG> This option tells <STRONG>tabs</STRONG> to check the options and run any debugging
98 option, but not to modify the terminal settings.
100 <STRONG>-V</STRONG> reports the version of ncurses which was used in this program, and
103 The <STRONG>tabs</STRONG> program processes a single list of tab stops. The last option
104 to be processed which defines a list is the one that determines the
105 list to be processed.
108 </PRE><H3><a name="h3-Implicit-Lists">Implicit Lists</a></H3><PRE>
109 Use a single number as an option, e.g., "<STRONG>-5</STRONG>" to set tabs at the given
110 interval (in this case 1, 6, 11, 16, 21, etc.). Tabs are repeated up
111 to the right margin of the screen.
113 Use "<STRONG>-0</STRONG>" to clear all tabs.
115 Use "<STRONG>-8</STRONG>" to set tabs to the standard interval.
118 </PRE><H3><a name="h3-Explicit-Lists">Explicit Lists</a></H3><PRE>
119 An explicit list can be defined after the options (this does not use a
120 "-"). The values in the list must be in increasing numeric order, and
121 greater than zero. They are separated by a comma or a blank, for
127 Use a "+" to treat a number as an increment relative to the previous
132 which is equivalent to the 1,6,11,16,21 example.
135 </PRE><H3><a name="h3-Predefined-Tab-Stops">Predefined Tab-Stops</a></H3><PRE>
136 POSIX defines several predefined lists of tab stops.
138 <STRONG>-a</STRONG> Assembler, IBM S/370, first format
141 <STRONG>-a2</STRONG> Assembler, IBM S/370, second format
144 <STRONG>-c</STRONG> COBOL, normal format
147 <STRONG>-c2</STRONG> COBOL compact format
150 <STRONG>-c3</STRONG> COBOL compact format extended
151 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
153 <STRONG>-f</STRONG> FORTRAN
156 <STRONG>-p</STRONG> PL/I
157 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
159 <STRONG>-s</STRONG> SNOBOL
162 <STRONG>-u</STRONG> UNIVAC 1100 Assembler
166 </PRE><H3><a name="h3-Margins">Margins</a></H3><PRE>
167 A few terminals provide the capability for changing their left/right
168 margins. The tabs program has an option to use this feature:
170 <STRONG>+m</STRONG> <EM>margin</EM>
171 The effect depends on whether the terminal has the margin
174 <STRONG>o</STRONG> If the terminal provides the capability for setting the left
175 margin, tabs uses this, and adjusts the available width for
178 <STRONG>o</STRONG> If the terminal does not provide the margin capabilities, tabs
179 imitates the effect, putting the tab stops at the appropriate
180 place on each line. The terminal's left-margin is not
183 If the <EM>margin</EM> parameter is omitted, the default is 10. Use <STRONG>+m0</STRONG> to
184 reset the left margin, i.e., to the left edge of the terminal's
185 display. Before setting a left-margin, tabs resets the margin to
186 reduce problems which might arise on moving the cursor before the
189 When setting or resetting the left-margin, tabs may reset the right-
193 </PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
194 <EM>IEEE</EM> <EM>Std</EM> <EM>1003.1/The</EM> <EM>Open</EM> <EM>Group</EM> <EM>Base</EM> <EM>Specifications</EM> <EM>Issue</EM> <EM>7</EM>
195 (POSIX.1-2008) describes a <STRONG>tabs</STRONG> utility. However
197 <STRONG>o</STRONG> This standard describes a <STRONG>+m</STRONG> option, to set a terminal's left-
198 margin. Very few of the entries in the terminal database provide
199 the <STRONG>smgl</STRONG> (<STRONG>set_left_margin</STRONG>) or <STRONG>smglp</STRONG> (<STRONG>set_left_margin_parm</STRONG>)
200 capability needed to support the feature.
202 <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for this utility,
203 unlike <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>.
205 The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not provided by
206 other implementations.
208 A <STRONG>tabs</STRONG> utility appeared in PWB/Unix 1.0 (1977). There was a reduced
209 version of the <STRONG>tabs</STRONG> utility in Unix 7th edition and in 3BSD (1979).
210 The latter supported a single "-n" option (to cause the first tab stop
211 to be set on the left margin). That option is not documented by POSIX.
213 The PWB/Unix <STRONG>tabs</STRONG> utility, which was included in System III (1980),
214 used built-in tables rather than the terminal database, to support a
215 half-dozen hardcopy terminal (printer) types. It also had built-in
216 logic to support the left-margin, as well as a feature for copying the
217 tab settings from a file.
219 Later versions of Unix, e.g., SVr4, added support for the terminal
220 database, but kept the tables to support the printers. In an earlier
221 development effort, the tab-stop initialization provided by <STRONG>tset</STRONG> (1982)
222 and incorporated into <STRONG>tput</STRONG> uses the terminal database,
224 The <STRONG>+m</STRONG> option was documented in the Base Specifications Issue 5
225 (Unix98, 1997), and omitted in Issue 6 (Unix03, 2004) without
226 documenting the rationale, though an introductory comment <EM>"and</EM>
227 <EM>optionally</EM> <EM>adjusts</EM> <EM>the</EM> <EM>margin"</EM> remains, overlooked in the removal. The
228 documented <STRONG>tabs</STRONG> utility in Issues 6 and later has no mechanism for
229 setting margins. The <STRONG>+m</STRONG> option in this implementation differs from the
230 feature in SVr4 by using terminal capabilities rather than built-in
233 POSIX documents no limits on the number of tab stops. Documentation
234 for other implementations states that there is a limit on the number of
235 tab stops (e.g., 20 in PWB/Unix's <STRONG>tabs</STRONG> utility). While some terminals
236 may not accept an arbitrary number of tab stops, this implementation
237 will attempt to set tab stops up to the right margin of the screen, if
238 the given list happens to be that long.
240 The <EM>Rationale</EM> section of the POSIX documentation goes into some detail
241 about the ways the committee considered redesigning the <STRONG>tabs</STRONG> and <STRONG>tput</STRONG>
242 utilities, without proposing an improved solution. It comments that
244 no known historical version of tabs supports the capability of
245 setting arbitrary tab stops.
247 However, the <EM>Explicit</EM> <EM>Lists</EM> described in this manual page were
248 implemented in PWB/Unix. Those provide the capability of setting
252 </PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
253 <STRONG><A HREF="infocmp.1m.html">infocmp(1m)</A></STRONG>, <STRONG><A HREF="tset.1.html">tset(1)</A></STRONG>, <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>.
255 This describes <STRONG>ncurses</STRONG> version 6.3 (patch 20220917).
259 <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
263 <li><a href="#h2-NAME">NAME</a></li>
264 <li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
265 <li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
266 <li><a href="#h2-OPTIONS">OPTIONS</a>
268 <li><a href="#h3-General-Options">General Options</a></li>
269 <li><a href="#h3-Implicit-Lists">Implicit Lists</a></li>
270 <li><a href="#h3-Explicit-Lists">Explicit Lists</a></li>
271 <li><a href="#h3-Predefined-Tab-Stops">Predefined Tab-Stops</a></li>
272 <li><a href="#h3-Margins">Margins</a></li>
275 <li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
276 <li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>