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tabs 1

tabs(1)                     General Commands Manual                    tabs(1)




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

       o   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.

       o   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

       infocmp(1m), tset(1), curses(3x), terminfo(5).

       This describes ncurses version 6.2 (patch 20210403).



                                                                       tabs(1)