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<H1 class="no-header">tabs 1</H1>
<PRE>
<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-NAME">NAME</a></H2><PRE>
<STRONG>tabs</STRONG> - 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>
</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 <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.
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 <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.
<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>-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.
</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 "<STRONG>-0</STRONG>" to clear all tabs.
Use "<STRONG>-8</STRONG>" 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
example,
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
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>
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 provide the capability for changing their left/right
margins. The tabs program has an option to use this feature:
<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, tabs uses this, and adjusts the available width for
tab-stops.
<STRONG>o</STRONG> If the terminal does not provide the margin capabilities, tabs
imitates the effect, putting the tab stops at the appropriate
place 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, i.e., to the left edge of the terminal's
display. Before setting a left-margin, tabs resets the margin to
reduce problems which might arise on moving the cursor before the
current left-margin.
When setting or resetting the left-margin, tabs may reset the right-
margin.
</PRE><H2><a name="h2-PORTABILITY">PORTABILITY</a></H2><PRE>
<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-
margin. 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><A HREF="tput.1.html">tput(1)</A></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 hardcopy terminal (printer) 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 to support the printers. In an earlier
development effort, the tab-stop initialization provided by <STRONG>tset</STRONG> (1982)
and incorporated into <STRONG>tput</STRONG> uses the terminal database,
The <STRONG>+m</STRONG> option was documented in the Base Specifications Issue 5
(Unix98, 1997), and omitted in Issue 6 (Unix03, 2004) without
documenting the rationale, though an introductory comment <EM>"and</EM>
<EM>optionally</EM> <EM>adjusts</EM> <EM>the</EM> <EM>margin"</EM> remains, overlooked in the removal. The
documented <STRONG>tabs</STRONG> utility in Issues 6 and later has no mechanism for
setting margins. The <STRONG>+m</STRONG> option in this implementation differs from the
feature in SVr4 by using terminal capabilities rather than built-in
tables.
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
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="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>.
This describes <STRONG>ncurses</STRONG> version 6.4 (patch 20221231).
<STRONG><A HREF="tabs.1.html">tabs(1)</A></STRONG>
</PRE>
<div class="nav">
<ul>
<li><a href="#h2-NAME">NAME</a></li>
<li><a href="#h2-SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#h2-DESCRIPTION">DESCRIPTION</a></li>
<li><a href="#h2-OPTIONS">OPTIONS</a>
<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-Margins">Margins</a></li>
</ul>
</li>
<li><a href="#h2-PORTABILITY">PORTABILITY</a></li>
<li><a href="#h2-SEE-ALSO">SEE ALSO</a></li>
</ul>
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