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- * @Id: tabs.1,v 1.19 2018/07/28 21:46:31 tom Exp @
+ * @Id: tabs.1,v 1.25 2019/06/15 23:08:12 tom Exp @
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ing the tabstops), and later <STRONG>cat</STRONG> the file to the screen, setting tab-
stops at that point.
+ These are hardware tabs, which cannot be queried rapidly by applica-
+ tions 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 <STRONG>reset</STRONG> program, since the normal initialization sequences do
+ not ensure that tab-stops are reset.
+
</PRE><H2><a name="h2-OPTIONS">OPTIONS</a></H2><PRE>
(POSIX.1-2008) describes a <STRONG>tabs</STRONG> 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.
+ gin. Very few of the entries in the terminal database provide the
+ <STRONG>smgl</STRONG> (<STRONG>set_left_margin</STRONG>) or <STRONG>smglp</STRONG> (<STRONG>set_left_margin_parm</STRONG>) capability
+ needed to support the feature.
- <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for this utility,
+ <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for this utility,
unlike <STRONG>tput(1)</STRONG>.
- The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not provided by
+ The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (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 <STRONG>tabs</STRONG> utility appeared in PWB/Unix 1.0 (1977), and thereafter in 3BSD
+ (1979). It 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.
+ Initially, <STRONG>tabs</STRONG> 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 set-
+ tings 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 develop-
+ ment effort, the tab-stop initialization provided by <STRONG>tset</STRONG> (1982) and
+ incorporated into <STRONG>tput</STRONG> 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. 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 <EM>Rationale</EM> section of the POSIX documentation goes into some detail
+ about the ways the committee considered redesigning the <STRONG>tabs</STRONG> and <STRONG>tput</STRONG>
+ 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 <EM>Explicit</EM> <EM>Lists</EM> described in this manual page were imple-
+ mented 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>.
- This describes <STRONG>ncurses</STRONG> version 6.1 (patch 20181208).
+ This describes <STRONG>ncurses</STRONG> version 6.1 (patch 20190615).
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