239 lines
8.2 KiB
Groff
239 lines
8.2 KiB
Groff
.\"***************************************************************************
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.\" Copyright 2018-2019,2020 Thomas E. Dickey *
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.\" Copyright 2008-2016,2017 Free Software Foundation, Inc. *
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.\" *
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.\" Permission is hereby granted, free of charge, to any person obtaining a *
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.\" copy of this software and associated documentation files (the *
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.\" "Software"), to deal in the Software without restriction, including *
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.\" without limitation the rights to use, copy, modify, merge, publish, *
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.\" distribute, distribute with modifications, sublicense, and/or sell *
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.\" copies of the Software, and to permit persons to whom the Software is *
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.\" furnished to do so, subject to the following conditions: *
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.\" *
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.\" The above copyright notice and this permission notice shall be included *
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.\" in all copies or substantial portions of the Software. *
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.\" *
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.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
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.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
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.\" IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
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.\" DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
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.\" OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
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.\" THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
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.\" *
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.\" Except as contained in this notice, the name(s) of the above copyright *
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.\" holders shall not be used in advertising or otherwise to promote the *
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.\" sale, use or other dealings in this Software without prior written *
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.\" authorization. *
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.\"***************************************************************************
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.\"
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.\" $Id: tabs.1,v 1.28 2020/12/19 21:50:22 tom Exp $
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.TH @TABS@ 1 ""
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.ds n 5
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.ie \n(.g .ds `` \(lq
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.el .ds `` ``
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.ie \n(.g .ds '' \(rq
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.el .ds '' ''
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.de bP
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.ie n .IP \(bu 4
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.el .IP \(bu 2
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..
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.de NS
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.ie n .sp
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.el .sp .5
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.ie n .in +4
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.el .in +2
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.nf
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.ft C \" Courier
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..
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.de NE
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.fi
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.ft R
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.ie n .in -4
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.el .in -2
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..
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.SH NAME
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\fB@TABS@\fR \- set tabs on a terminal
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.SH SYNOPSIS
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\fB@TABS@\fR [\fIoptions\fR]] \fI[tabstop-list]\fR
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.SH DESCRIPTION
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.PP
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The \fB@TABS@\fP program clears and sets tab-stops on the terminal.
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This uses the terminfo \fIclear_all_tabs\fP and \fIset_tab\fP capabilities.
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If either is absent, \fB@TABS@\fP is unable to clear/set tab-stops.
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The terminal should be configured to use hard tabs, e.g.,
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.NS
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stty tab0
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.NE
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.PP
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Like \fB@CLEAR@\fR(1), \fB@TABS@\fR writes to the standard output.
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You can redirect the standard output to a file (which prevents
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\fB@TABS@\fR from actually changing the tabstops),
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and later \fBcat\fP the file to the screen, setting tabstops at that point.
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.PP
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These are hardware tabs, which cannot be queried rapidly by applications
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running in the terminal, if at all.
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Curses and other full-screen applications may use hardware tabs
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in optimizing their output to the terminal.
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If the hardware tabstops differ from the information in the terminal
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database, the result is unpredictable.
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Before running curses programs,
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you should either reset tab-stops to the standard interval
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.NS
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tabs -8
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.NE
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.PP
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or use the \fB@RESET@\fP program,
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since the normal initialization sequences do not ensure that tab-stops
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are reset.
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.SH OPTIONS
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.SS General Options
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.TP 5
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.BI \-T "name"
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Tell \fB@TABS@\fP which terminal type to use.
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If this option is not given, \fB@TABS@\fP will use the \fB$TERM\fP
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environment variable.
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If that is not set, it will use the \fIansi+tabs\fP entry.
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.TP 5
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.B \-d
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The debugging option shows a ruler line, followed by two data lines.
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The first data line shows the expected tab-stops marked with asterisks.
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The second data line shows the actual tab-stops, marked with asterisks.
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.TP 5
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.B \-n
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This option tells \fB@TABS@\fP to check the options and run any debugging
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option, but not to modify the terminal settings.
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.TP
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\fB\-V\fR
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reports the version of ncurses which was used in this program, and exits.
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.PP
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The \fB@TABS@\fP program processes a single list of tab stops.
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The last option to be processed which defines a list is the one that
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determines the list to be processed.
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.SS Implicit Lists
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Use a single number as an option,
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e.g., \*(``\fB\-5\fP\*('' to set tabs at the given
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interval (in this case 1, 6, 11, 16, 21, etc.).
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Tabs are repeated up to the right margin of the screen.
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.PP
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Use \*(``\fB\-0\fP\*('' to clear all tabs.
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.PP
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Use \*(``\fB\-8\fP\*('' to set tabs to the standard interval.
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.SS Explicit Lists
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An explicit list can be defined after the options
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(this does not use a \*(``\-\*('').
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The values in the list must be in increasing numeric order,
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and greater than zero.
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They are separated by a comma or a blank, for example,
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.NS
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tabs 1,6,11,16,21
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.br
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tabs 1 6 11 16 21
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.NE
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.PP
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Use a \*(``+\*('' to treat a number
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as an increment relative to the previous value,
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e.g.,
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.NS
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tabs 1,+5,+5,+5,+5
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.NE
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.PP
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which is equivalent to the 1,6,11,16,21 example.
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.SS Predefined Tab-Stops
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X/Open defines several predefined lists of tab stops.
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.TP 5
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.B \-a
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Assembler, IBM S/370, first format
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.TP 5
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.B \-a2
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Assembler, IBM S/370, second format
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.TP 5
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.B \-c
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COBOL, normal format
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.TP 5
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.B \-c2
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COBOL compact format
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.TP 5
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.B \-c3
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COBOL compact format extended
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.TP 5
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.B \-f
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FORTRAN
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.TP 5
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.B \-p
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PL/I
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.TP 5
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.B \-s
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SNOBOL
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.TP 5
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.B \-u
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UNIVAC 1100 Assembler
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.SH PORTABILITY
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.PP
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\fIIEEE Std 1003.1/The Open Group Base Specifications Issue 7\fP (POSIX.1-2008)
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describes a \fBtabs\fP utility.
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However
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.bP
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This standard describes a \fB+m\fP option, to set a terminal's left-margin.
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Very few of the entries in the terminal database provide the
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\fBsmgl\fP (\fBset_left_margin\fP) or
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\fBsmglp\fP (\fBset_left_margin_parm\fP)
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capability needed to support the feature.
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.bP
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There is no counterpart in X/Open Curses Issue 7 for this utility,
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unlike \fB@TPUT@(1)\fP.
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.PP
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The \fB\-d\fP (debug) and \fB\-n\fP (no-op) options are extensions not provided
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by other implementations.
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.PP
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A \fBtabs\fP utility appeared in PWB/Unix 1.0 (1977).
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There was a reduced version of the \fBtabs\fP utility
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in Unix 7th edition and in 3BSD (1979).
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The latter supported a single \*(``\-n\*('' option
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(to cause the first tab stop to be set on the left margin).
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That option is not documented by POSIX.
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.PP
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The PWB/Unix \fBtabs\fP utility, which was included in System III (1980),
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used built-in tables rather than the terminal database,
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to support a half-dozen terminal types.
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It also had built-in logic to support the left-margin,
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as well as a feature for copying the tab settings from a file.
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.PP
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Later versions of Unix, e.g., SVr4,
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added support for the terminal database,
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but kept the tables, as a fallback.
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In an earlier development effort,
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the tab-stop initialization provided by \fBtset\fP (1982)
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and incorporated into \fBtput\fP uses the terminal database,
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.PP
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POSIX documents no limits on the number of tab stops.
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Documentation for other implementations states that there is a limit on the
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number of tab stops
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(e.g., 20 in PWB/Unix's \fBtabs\fP utility).
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While some terminals may not accept an arbitrary number
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of tab stops, this implementation will attempt to set tab stops up to the
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right margin of the screen, if the given list happens to be that long.
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.PP
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The \fIRationale\fP section of the POSIX documentation goes into some
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detail about the ways the committee considered redesigning the
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\fBtabs\fP and \fBtput\fP utilities,
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without proposing an improved solution.
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It comments that
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.RS 5
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.PP
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no known historical version of tabs supports the capability of setting
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arbitrary tab stops.
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.RE
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.PP
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However, the \fIExplicit Lists\fP described in this manual page
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were implemented in PWB/Unix.
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Those provide the capability of setting abitrary tab stops.
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.SH SEE ALSO
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\fB@INFOCMP@\fR(1M),
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\fB@TSET@\fR(1),
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\fBcurses\fR(3X),
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\fBterminfo\fR(\*n).
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.PP
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This describes \fBncurses\fR
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version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch @NCURSES_PATCH@).
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