Provided by: ncurses-bin_6.3-2ubuntu0.1_amd64 bug


       tabs - set tabs on a terminal


       tabs [options]] [tabstop-list]


       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.


   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 feature:

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

            •   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 right-margin.


       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

       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

       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

       However, the Explicit Lists described in this manual page were  implemented  in  PWB/Unix.
       Those provide the capability of setting abitrary tab stops.


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

       This describes ncurses version 6.3 (patch 20211021).