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<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>
+<STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
General Commands Manual <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
absent, <STRONG>tabs</STRONG> 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.
+ 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>
greater than zero. They are separated by a comma or a blank, for exam-
ple,
- 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
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><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
- IEEE Std 1003.1/The Open Group Base Specifications Issue 7
+ <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>
(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). There was a reduced
+ version of the <STRONG>tabs</STRONG> 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 <STRONG>tabs</STRONG> 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 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 (e.g., 20 in PWB/Unix's <STRONG>tabs</STRONG> 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 <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 6.0 (patch 20170506).
+ This describes <STRONG>ncurses</STRONG> version 6.2 (patch 20200725).
projects / ncurses.git / blobdiff