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)