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+ * Copyright 2018-2019,2020 Thomas E. Dickey *
+ * Copyright 2008-2016,2017 Free Software Foundation, Inc. *
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- * @Id: tabs.1,v 1.15 2016/12/31 16:07:39 tom Exp @
+ * @Id: tabs.1,v 1.28 2020/12/19 21:50:22 tom Exp @
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-<H1 class="no-header">tabs 1</H1>
+<H1 class="no-header">@TABS@ 1</H1>
<PRE>
-<STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG> <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
+<B><A HREF="tabs.1.html">tabs(1)</A></B> General Commands Manual <B><A HREF="tabs.1.html">tabs(1)</A></B>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
- <STRONG>tabs</STRONG> - set tabs on a terminal
+ <B>tabs</B> - set tabs on a terminal
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
- <STRONG>tabs</STRONG> [<EM>options</EM>]] <EM>[tabstop-list]</EM>
+ <B>tabs</B> [<I>options</I>]] <I>[tabstop-list]</I>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
- The <STRONG>tabs</STRONG> program clears and sets tab-stops on the terminal. This uses
- the terminfo <EM>clear</EM><STRONG>_</STRONG><EM>all</EM><STRONG>_</STRONG><EM>tabs</EM> and <EM>set</EM><STRONG>_</STRONG><EM>tab</EM> capabilities. If either is
- absent, <STRONG>tabs</STRONG> is unable to clear/set tab-stops. The terminal should be
+ The <B>tabs</B> program clears and sets tab-stops on the terminal. This uses
+ the terminfo <I>clear</I><B>_</B><I>all</I><B>_</B><I>tabs</I> and <I>set</I><B>_</B><I>tab</I> capabilities. If either is
+ absent, <B>tabs</B> is unable to clear/set tab-stops. The terminal should be
configured to use hard tabs, e.g.,
- stty tab0
+ stty tab0
- Like <STRONG><A HREF="clear.1.html">clear(1)</A></STRONG>, <STRONG>tabs</STRONG> writes to the standard output. You can redirect
- the standard output to a file (which prevents <STRONG>tabs</STRONG> from actually chang-
- ing the tabstops), and later <STRONG>cat</STRONG> the file to the screen, setting tab-
- stops at that point.
+ Like <B><A HREF="clear.1.html">clear(1)</A></B>, <B>tabs</B> writes to the standard output. You can redirect
+ the standard output to a file (which prevents <B>tabs</B> from actually
+ changing the tabstops), and later <B>cat</B> the file to the screen, setting
+ tabstops at that point.
+
+ These are hardware tabs, which cannot be queried rapidly by
+ applications running in the terminal, if at all. Curses and other
+ full-screen applications may use hardware tabs in optimizing their
+ output to the terminal. If the hardware tabstops differ from the
+ information in the terminal database, the result is unpredictable.
+ Before running curses programs, you should either reset tab-stops to
+ the standard interval
+
+ tabs -8
+
+ or use the <B>reset</B> program, since the normal initialization sequences do
+ not ensure that tab-stops are reset.
</PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
</PRE><H3><a name="h3-General-Options">General Options</a></H3><PRE>
- <STRONG>-T</STRONG><EM>name</EM>
- Tell <STRONG>tabs</STRONG> which terminal type to use. If this option is not
- given, <STRONG>tabs</STRONG> will use the <STRONG>$TERM</STRONG> environment variable. If that is
- not set, it will use the <EM>ansi+tabs</EM> entry.
-
- <STRONG>-d</STRONG> The debugging option shows a ruler line, followed by two data
- lines. The first data line shows the expected tab-stops marked
- with asterisks. The second data line shows the actual tab-stops,
+ <B>-T</B><I>name</I>
+ Tell <B>tabs</B> which terminal type to use. If this option is not
+ given, <B>tabs</B> will use the <B>$TERM</B> environment variable. If that is
+ not set, it will use the <I>ansi+tabs</I> entry.
+
+ <B>-d</B> The debugging option shows a ruler line, followed by two data
+ lines. The first data line shows the expected tab-stops marked
+ with asterisks. The second data line shows the actual tab-stops,
marked with asterisks.
- <STRONG>-n</STRONG> This option tells <STRONG>tabs</STRONG> to check the options and run any debugging
+ <B>-n</B> This option tells <B>tabs</B> to check the options and run any debugging
option, but not to modify the terminal settings.
- <STRONG>-V</STRONG> reports the version of ncurses which was used in this program, and
+ <B>-V</B> reports the version of ncurses which was used in this program, and
exits.
- The <STRONG>tabs</STRONG> program processes a single list of tab stops. The last option
- to be processed which defines a list is the one that determines the
+ The <B>tabs</B> program processes a single list of tab stops. The last option
+ to be processed which defines a list is the one that determines the
list to be processed.
</PRE><H3><a name="h3-Implicit-Lists">Implicit Lists</a></H3><PRE>
- Use a single number as an option, e.g., "<STRONG>-5</STRONG>" to set tabs at the given
- interval (in this case 1, 6, 11, 16, 21, etc.). Tabs are repeated up
+ Use a single number as an option, e.g., "<B>-5</B>" to set tabs at the given
+ interval (in this case 1, 6, 11, 16, 21, etc.). Tabs are repeated up
to the right margin of the screen.
- Use "<STRONG>-0</STRONG>" to clear all tabs.
+ Use "<B>-0</B>" to clear all tabs.
- Use "<STRONG>-8</STRONG>" to set tabs to the standard interval.
+ Use "<B>-8</B>" to set tabs to the standard interval.
</PRE><H3><a name="h3-Explicit-Lists">Explicit Lists</a></H3><PRE>
- An explicit list can be defined after the options (this does not use a
- "-"). The values in the list must be in increasing numeric order, and
- greater than zero. They are separated by a comma or a blank, for exam-
- ple,
+ An explicit list can be defined after the options (this does not use a
+ "-"). The values in the list must be in increasing numeric order, and
+ greater than zero. They are separated by a comma or a blank, for
+ example,
- tabs 1,6,11,16,21
- tabs 1 6 11 16 21
+ tabs 1,6,11,16,21
+ tabs 1 6 11 16 21
- Use a "+" to treat a number as an increment relative to the previous
+ Use a "+" to treat a number as an increment relative to the previous
value, e.g.,
- tabs 1,+5,+5,+5,+5
+ tabs 1,+5,+5,+5,+5
which is equivalent to the 1,6,11,16,21 example.
</PRE><H3><a name="h3-Predefined-Tab-Stops">Predefined Tab-Stops</a></H3><PRE>
X/Open defines several predefined lists of tab stops.
- <STRONG>-a</STRONG> Assembler, IBM S/370, first format
+ <B>-a</B> Assembler, IBM S/370, first format
- <STRONG>-a2</STRONG> Assembler, IBM S/370, second format
+ <B>-a2</B> Assembler, IBM S/370, second format
- <STRONG>-c</STRONG> COBOL, normal format
+ <B>-c</B> COBOL, normal format
- <STRONG>-c2</STRONG> COBOL compact format
+ <B>-c2</B> COBOL compact format
- <STRONG>-c3</STRONG> COBOL compact format extended
+ <B>-c3</B> COBOL compact format extended
- <STRONG>-f</STRONG> FORTRAN
+ <B>-f</B> FORTRAN
- <STRONG>-p</STRONG> PL/I
+ <B>-p</B> PL/I
- <STRONG>-s</STRONG> SNOBOL
+ <B>-s</B> SNOBOL
- <STRONG>-u</STRONG> UNIVAC 1100 Assembler
+ <B>-u</B> UNIVAC 1100 Assembler
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
- IEEE Std 1003.1/The Open Group Base Specifications Issue 7
- (POSIX.1-2008) describes a <STRONG>tabs</STRONG> utility. However
+ <I>IEEE</I> <I>Std</I> <I>1003.1/The</I> <I>Open</I> <I>Group</I> <I>Base</I> <I>Specifications</I> <I>Issue</I> <I>7</I>
+ (POSIX.1-2008) describes a <B>tabs</B> utility. However
- <STRONG>o</STRONG> This standard describes a <STRONG>+m</STRONG> option, to set a terminal's left-mar-
- gin. Very few of the entries in the terminal database provide this
- capability.
+ <B>o</B> This standard describes a <B>+m</B> option, to set a terminal's left-
+ margin. Very few of the entries in the terminal database provide
+ the <B>smgl</B> (<B>set_left_margin</B>) or <B>smglp</B> (<B>set_left_margin_parm</B>)
+ capability needed to support the feature.
- <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for this utility,
- unlike <STRONG>tput(1)</STRONG>.
+ <B>o</B> There is no counterpart in X/Open Curses Issue 7 for this utility,
+ unlike <B>tput(1)</B>.
- The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not provided by
+ The <B>-d</B> (debug) and <B>-n</B> (no-op) options are extensions not provided by
other implementations.
- Documentation for other implementations states that there is a limit on
- the number of tab stops. While some terminals may not accept an arbi-
- trary number of tab stops, this implementation will attempt to set tab
- stops up to the right margin of the screen, if the given list happens
- to be that long.
+ A <B>tabs</B> utility appeared in PWB/Unix 1.0 (1977). There was a reduced
+ version of the <B>tabs</B> utility in Unix 7th edition and in 3BSD (1979).
+ The latter supported a single "-n" option (to cause the first tab stop
+ to be set on the left margin). That option is not documented by POSIX.
+
+ The PWB/Unix <B>tabs</B> utility, which was included in System III (1980),
+ used built-in tables rather than the terminal database, to support a
+ half-dozen terminal types. It also had built-in logic to support the
+ left-margin, as well as a feature for copying the tab settings from a
+ file.
+
+ Later versions of Unix, e.g., SVr4, added support for the terminal
+ database, but kept the tables, as a fallback. In an earlier
+ development effort, the tab-stop initialization provided by <B>tset</B> (1982)
+ and incorporated into <B>tput</B> uses the terminal database,
+
+ POSIX documents no limits on the number of tab stops. Documentation
+ for other implementations states that there is a limit on the number of
+ tab stops (e.g., 20 in PWB/Unix's <B>tabs</B> utility). While some terminals
+ may not accept an arbitrary number of tab stops, this implementation
+ will attempt to set tab stops up to the right margin of the screen, if
+ the given list happens to be that long.
+
+ The <I>Rationale</I> section of the POSIX documentation goes into some detail
+ about the ways the committee considered redesigning the <B>tabs</B> and <B>tput</B>
+ utilities, without proposing an improved solution. It comments that
+
+ no known historical version of tabs supports the capability of
+ setting arbitrary tab stops.
+
+ However, the <I>Explicit</I> <I>Lists</I> described in this manual page were
+ implemented in PWB/Unix. Those provide the capability of setting
+ abitrary tab stops.
</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
- <STRONG><A HREF="tset.1.html">tset(1)</A></STRONG>, <STRONG><A HREF="infocmp.1m.html">infocmp(1m)</A></STRONG>, <STRONG><A HREF="ncurses.3x.html">curses(3x)</A></STRONG>, <STRONG><A HREF="terminfo.5.html">terminfo(5)</A></STRONG>.
+ <B><A HREF="infocmp.1M.html">infocmp(1M)</A></B>, <B><A HREF="tset.1.html">tset(1)</A></B>, <B><A HREF="curses.3X.html">curses(3X)</A></B>, <B><A HREF="terminfo.5.html">terminfo(5)</A></B>.
- This describes <STRONG>ncurses</STRONG> version 6.0 (patch 20170812).
+ This describes <B>ncurses</B> version 6.2 (patch 20210612).
- <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
+ <B><A HREF="tabs.1.html">tabs(1)</A></B>
</PRE>
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