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+ * Copyright 2018-2023,2024 Thomas E. Dickey *
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-<H1 class="no-header">tabs 1</H1>
+<H1 class="no-header">tabs 1 2024-04-20 ncurses 6.4 User commands</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>
User commands <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
</PRE><H2><a name="h2-NAME">NAME</a></H2><PRE>
- <STRONG>tabs</STRONG> - set tabs on a terminal
+ <STRONG>tabs</STRONG> - set terminal tab stops
</PRE><H2><a name="h2-SYNOPSIS">SYNOPSIS</a></H2><PRE>
- <STRONG>tabs</STRONG> [<EM>options</EM>]] <EM>[tabstop-list]</EM>
+ <STRONG>tabs</STRONG> [<EM>options</EM>] [<EM>tabstop-list</EM>]
</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 <STRONG>clear_all_tabs</STRONG> and <STRONG>set_tab</STRONG> 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
+
+ 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
+ changing the tabstops), and later <STRONG>cat</STRONG> the file to the screen, setting
+ tabstops at that point.
- stty tab0
+ 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
- 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 changing the tabstops), and later <STRONG>cat</STRONG>
- the file to the screen, setting tabstops at that point.
+ 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 <EM>ncurses</EM> 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
+ 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 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><H3><a name="h3-Predefined-Tab-Stops">Predefined Tab
-Stops</a></H3><PRE>
- X/Open defines several predefined lists of tab stops.
+</PRE><H3><a name="h3-Predefined-Tab-Stops">Predefined Tab
Stops</a></H3><PRE>
+ POSIX defines several predefined lists of tab stops.
<STRONG>-a</STRONG> Assembler, IBM S/370, first format
+ 1,10,16,36,72
<STRONG>-a2</STRONG> Assembler, IBM S/370, second format
+ 1,10,16,40,72
<STRONG>-c</STRONG> COBOL, normal format
+ 1,8,12,16,20,55
<STRONG>-c2</STRONG> COBOL compact format
+ 1,6,10,14,49
<STRONG>-c3</STRONG> COBOL compact format extended
+ 1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
<STRONG>-f</STRONG> FORTRAN
+ 1,7,11,15,19,23
<STRONG>-p</STRONG> PL/I
+ 1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
<STRONG>-s</STRONG> SNOBOL
+ 1,10,55
<STRONG>-u</STRONG> UNIVAC 1100 Assembler
+ 1,12,20,44
+
+
+</PRE><H3><a name="h3-Margins">Margins</a></H3><PRE>
+ A few terminals expose a means of changing their left and right
+ margins. <STRONG>tabs</STRONG> supports this feature with an option.
+
+ <STRONG>+m</STRONG> <EM>margin</EM>
+ The effect depends on whether the terminal has the margin
+ capabilities:
+
+ <STRONG>o</STRONG> If the terminal provides the capability for setting the left
+ margin, <STRONG>tabs</STRONG> uses this, and adjusts the available tab stop
+ widths.
+
+ <STRONG>o</STRONG> If the terminal does not provide the margin capabilities, <STRONG>tabs</STRONG>
+ imitates their effect, putting tab stops at appropriate places
+ on each line. The terminal's left margin is not modified.
+
+ If the <EM>margin</EM> parameter is omitted, the default is 10. Use <STRONG>+m0</STRONG> to
+ reset the left margin, that is, to make it the left edge of the
+ terminal's display. Before setting a left margin, <STRONG>tabs</STRONG> resets the
+ margin to reduce problems that might arise from moving the cursor
+ to the left of the current left margin.
+
+ When setting or resetting the left margin, <STRONG>tabs</STRONG> may also reset the
+ right margin.
+
+
+</PRE><H2><a name="h2-FILES">FILES</a></H2><PRE>
+ <EM>/usr/share/tabset</EM>
+ tab stop initialization database
</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
+ IEEE Std 1003.1/The Open Group Base Specifications Issue 7
+ (POSIX.1-2008) describes a <STRONG>tabs</STRONG> utility. However,
- <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.
+ <STRONG>o</STRONG> this standard describes a <STRONG>+m</STRONG> option to set a terminal's left
+ margin. Very few of the entries in the terminal database provide
+ the <STRONG>set_left_margin</STRONG> (<STRONG>smgl</STRONG>) or <STRONG>set_left_margin_parm</STRONG> (<STRONG>smglp</STRONG>)
+ capabilities 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>.
+ <STRONG>o</STRONG> There is no counterpart in X/Open Curses Issue 7 for this utility,
+ unlike <STRONG><A HREF="tput.1.html">tput(1)</A></STRONG>.
- The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are extensions not
+ The <STRONG>-d</STRONG> (debug) and <STRONG>-n</STRONG> (no-op) options are <EM>ncurses</EM> extensions not
provided by other implementations.
- 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.
+</PRE><H2><a name="h2-HISTORY">HISTORY</a></H2><PRE>
+ A <STRONG>tabs</STRONG> utility appeared in PWB/Unix 1.0 (1977). A reduced version
+ shipped in Seventh Edition Unix (early 1979) and in 3BSD (later the
+ same year); it supported a "-n" option to set the first tab stop at the
+ left margin. That option is not specified by POSIX.
-</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>.
+ The PWB/Unix <STRONG>tabs</STRONG> utility returned in System III (1980), and used
+ built-in tables to support a half-dozen hardcopy terminal (printer)
+ types. It also had logic to support setting the left margin, as well
+ as a feature for copying the tab settings from a file.
+
+ Versions of the program in later releases of AT&T Unix, such as SVr4,
+ added support for the terminal database, but retained the tables to
+ support the printers. By this time, System V <STRONG>tput</STRONG> had incorporated the
+ tab stop initialization feature of BSD's <STRONG>tset</STRONG> from 1982, but employed
+ the <EM>terminfo</EM> database to do so.
+
+ The <STRONG>+m</STRONG> option was documented in the POSIX Base Specifications Issue 5
+ (Unix98, 1997), then omitted in Issue 6 (Unix03, 2004) without express
+ motivation, though an introductory comment "and optionally adjusts the
+ margin" remains, overlooked in the removal. The <STRONG>tabs</STRONG> utility
+ documented in Issues 6 and later has no mechanism for setting margins.
+ The <STRONG>+m</STRONG> option in <EM>ncurses</EM> <STRONG>tabs</STRONG> differs from the SVr4 feature by using
+ terminal capabilities rather than built-in tables.
+
+ POSIX documents no limit on the number of tab stops. Other
+ implementations impose one; the limit is 20 in PWB/Unix's <STRONG>tabs</STRONG> utility.
+ While some terminals may not accept an arbitrary number of tab stops,
+ <EM>ncurses</EM> <STRONG>tabs</STRONG> attempts to set tab stops up to the right margin if the
+ list thereof is sufficiently long.
- This describes <STRONG>ncurses</STRONG> version 6.0 (patch 20170128).
+ The "Rationale" section of the Issue 6 <STRONG>tabs</STRONG> reference page details how
+ the committee considered redesigning the <STRONG>tabs</STRONG> and <STRONG>tput</STRONG> utilities,
+ without settling on an improved solution. It claims that
+
+ "no known historical version of <EM>tabs</EM> supports the capability of
+ setting arbitrary tab stops."
+
+ The feature described in subsection "Explicit Lists" above was
+ implemented in PWB/Unix, and permitted the setting of abitrary tab
+ stops nevertheless.
+
+
+</PRE><H2><a name="h2-SEE-ALSO">SEE ALSO</a></H2><PRE>
+ <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>
-
<STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
+
ncurses 6.4 2024-04-20 <STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h3-General-Options">General Options</a></li>
<li><a href="#h3-Implicit-Lists">Implicit Lists</a></li>
<li><a href="#h3-Explicit-Lists">Explicit Lists</a></li>
-<li><a href="#h3-Predefined-Tab-Stops">Predefined Tab-Stops</a></li>
+<li><a href="#h3-Predefined-Tab-Stops">Predefined Tab Stops</a></li>
+<li><a href="#h3-Margins">Margins</a></li>
</ul>
</li>
+<li><a href="#h2-FILES">FILES</a></li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
+<li><a href="#h2-HISTORY">HISTORY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
</div>
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