tabs(1) — Linux manual page


@TABS@(1)                  General Commands Manual                 @TABS@(1)

NAME         top

       @TABS@ - set tabs on a terminal

SYNOPSIS         top

       @TABS@ [options]] [tabstop-list]

DESCRIPTION         top

       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.

OPTIONS         top

   General Options
            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

           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
       X/Open defines several predefined lists of tab stops.

       -a   Assembler, IBM S/370, first format

       -a2  Assembler, IBM S/370, second format

       -c   COBOL, normal format

       -c2  COBOL compact format

       -c3  COBOL compact format extended

       -f   FORTRAN

       -p   PL/I

       -s   SNOBOL

       -u   UNIVAC 1100 Assembler

PORTABILITY         top

       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

       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 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

       Later versions of Unix, e.g., SVr4, added support for the terminal
       database, but kept the tables, as a fallback.  In an earlier
       development effort, the tab-stop initialization provided by tset
       (1982) and incorporated into tput 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 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.

SEE ALSO         top

       @TSET@(1), @INFOCMP@(1M), curses(3X), terminfo(5).

       This describes ncurses version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch

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