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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>
</PRE><H2><a name="h2-DESCRIPTION">DESCRIPTION</a></H2><PRE>
- The <STRONG>tabs</STRONG> program clears and sets tab-stops on the termi-
- nal. 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 configured to
- use hard tabs, e.g.,
+ 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
+ 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>
</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>$TERM</STRONG> environment
- variable. If that is not set, it will use the
- <EM>ansi+tabs</EM> entry.
+ Tell <STRONG>tabs</STRONG> which terminal type to use. If this option is not
+ given, <STRONG>tabs</STRONG> will use the <STRONG>$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, marked with
- asterisks.
+ <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,
+ marked with asterisks.
- <STRONG>-n</STRONG> This option tells <STRONG>tabs</STRONG> to check the options and run
- any debugging option, but not to modify the terminal
- settings.
+ <STRONG>-n</STRONG> This option tells <STRONG>tabs</STRONG> 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 exits.
+ <STRONG>-V</STRONG> 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 list to be processed.
+ 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
+ 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 to the right margin of the
- screen.
+ 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
+ to the right margin of the screen.
Use "<STRONG>-0</STRONG>" to clear all tabs.
</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 example,
+ 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,
+
+ 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.,
+ 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 (POSIX.1-2008) describes a <STRONG>tabs</STRONG> utility. However
+ <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 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,
+ unlike <STRONG>tput(1)</STRONG>.
+
+ The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not provided by
+ other implementations.
+
+ 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,
- <STRONG>o</STRONG> This standard describes a <STRONG>+m</STRONG> option, to set a termi-
- nal's left-margin. Very few of the entries in the
- terminal database provide this capability.
+ 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.
- <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for
- this utility, unlike <STRONG><A HREF="tput.3x.html">tput(3x)</A></STRONG>.
+ 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
- The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not
- provided by other implementations.
+ no known historical version of tabs supports the capability of
+ setting arbitrary tab stops.
- Documentation for other implementations states that there
- is a limit on the number of tab stops. While some termi-
- nals 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.
+ 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 20160611).
+ This describes <STRONG>ncurses</STRONG> version 6.1 (patch 20191026).
- <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
+
<STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
</PRE>
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