NAME

       tabs - set tabs on a terminal

SYNOPSIS

       tabs [options]] [tabstop-list]

DESCRIPTION

       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

   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
       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

       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 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 file.

       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

       tset(1), infocmp(1), ncurses(3NCURSES), terminfo(5).

       This describes ncurses version 6.2 (patch 20200212).

                                                                                                         tabs(1)