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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | PORTABILITY | SEE ALSO | COLOPHON |
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@TABS@(1) General Commands Manual @TABS@(1)
@TABS@ - set tabs on a terminal
@TABS@ [options]] [tabstop-list]
The @TABS@ program clears and sets tab-stops on the terminal.
This uses the terminfo clear_all_tabs and set_tab capabilities.
If either is absent, @TABS@ is unable to clear/set tab-stops.
The terminal should be configured to use hard tabs, e.g.,
stty tab0
Like @CLEAR@(1), @TABS@ writes to the standard output. You can
redirect the standard output to a file (which prevents @TABS@
from actually changing the tabstops), and later cat 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 @RESET@ program, since the normal initialization
sequences do not ensure that tab-stops are reset.
General Options
-Tname
Tell @TABS@ which terminal type to use. If this option is
not given, @TABS@ will use the $TERM environment variable.
If that is not set, it will use the ansi+tabs entry.
-d 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.
-n This option tells @TABS@ to check the options and run any
debugging option, but not to modify the terminal settings.
-V reports the version of ncurses which was used in this
program, and exits.
The @TABS@ 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.
Implicit Lists
Use a single number as an option, e.g., “-5” 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 “-0” to clear all tabs.
Use “-8” to set tabs to the standard interval.
Explicit Lists
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.
Predefined Tab-Stops
POSIX defines several predefined lists of tab stops.
-a Assembler, IBM S/370, first format
1,10,16,36,72
-a2 Assembler, IBM S/370, second format
1,10,16,40,72
-c COBOL, normal format
1,8,12,16,20,55
-c2 COBOL compact format
1,6,10,14,49
-c3 COBOL compact format extended
1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67
-f FORTRAN
1,7,11,15,19,23
-p PL/I
1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61
-s SNOBOL
1,10,55
-u UNIVAC 1100 Assembler
1,12,20,44
Margins
A few terminals provide the capability for changing their
left/right margins. The @TABS@ program has an option to use this
feature:
+m margin
The effect depends on whether the terminal has the margin
capabilities:
• If the terminal provides the capability for setting the
left margin, @TABS@ uses this, and adjusts the available
width for tab-stops.
• 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 margin parameter is omitted, the default is 10. Use
+m0 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.
IEEE Std 1003.1/The Open Group Base Specifications Issue 7
(POSIX.1-2008) describes a tabs utility. However
• This standard describes a +m option, to set a terminal's
left-margin. Very few of the entries in the terminal
database provide the smgl (set_left_margin) or smglp
(set_left_margin_parm) capability needed to support the
feature.
• There is no counterpart in X/Open Curses Issue 7 for this
utility, unlike @TPUT@(1).
The -d (debug) and -n (no-op) options are extensions not provided
by other implementations.
A tabs utility appeared in PWB/Unix 1.0 (1977). There was a
reduced version of the tabs 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 tabs 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 tset (1982) and incorporated into tput uses the
terminal database,
The +m 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 “and
optionally adjusts the margin” remains, overlooked in the
removal. The documented tabs utility in Issues 6 and later has
no mechanism for setting margins. The +m 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 tabs
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 Rationale section of the POSIX documentation goes into some
detail about the ways the committee considered redesigning the
tabs and tput 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 Explicit Lists described in this manual page were
implemented in PWB/Unix. Those provide the capability of setting
abitrary tab stops.
@INFOCMP@(1M), @TSET@(1), curses(3X), terminfo(5).
This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@
(patch @NCURSES_PATCH@).
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have
a bug report for this manual page, send it to
bug-ncurses-request@gnu.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
@TABS@(1)
Pages that refer to this page: terminfo(5)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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