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 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

       -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

       A few terminals provide the capability for changing their
       left/right margins.  The @TABS@ program has an option to use this

       +m margin
            The effect depends on whether the terminal has the margin

            •   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

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

       •   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.

SEE ALSO         top

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

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

COLOPHON         top

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