manpagez: man pages & more
man tabs(1)
Home | html | info | man
tabs(1)                                                                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 chang-
       ing the tabstops), and later cat the file to the screen,  setting  tab-
       stops at that point.

       These  are  hardware  tabs, which cannot be queried rapidly by applica-
       tions 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 exam-
       ple,

           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
            1,10,16,36,72

       -a2  Assembler, IBM S/370, second format
            1,10,16,40,72

       -c   COBOL, normal format
            1,8,12,16,20,55

       -c2  COBOL compact format
            1,6,10,14,49

       -c3  COBOL compact format extended
            1,6,10,14,18,22,26,30,34,38,42,46,50,54,58,62,67

       -f   FORTRAN
            1,7,11,15,19,23

       -p   PL/I
            1,5,9,13,17,21,25,29,33,37,41,45,49,53,57,61

       -s   SNOBOL
            1,10,55

       -u   UNIVAC 1100 Assembler
            1,12,20,44

   Margins
       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 capabil-
            ities:

            o   If the terminal provides the capability for setting  the  left
                margin,  tabs  uses  this, and adjusts the available width for
                tab-stops.

            o   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  modi-
                fied.

            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.


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-mar-
           gin.  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 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 document-
       ing  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 mar-
       gins.  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 imple-
       mented 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 6.3 (patch 20211021).



                                                                       tabs(1)

ncurses 6.3 - Generated Thu Nov 11 18:45:14 CST 2021
© manpagez.com 2000-2022
Individual documents may contain additional copyright information.