ncurses 6.5 - patch 20240525

[ncurses.git] / man / clear.1

diff --git a/man/clear.1 b/man/clear.1
index 9748fdd5a3aa29bc8b7092a84267a5abcc23245e..a1034db7cb1a98ce34fc8a13063fc1e81d4b3e2a 100644 (file)
--- a/man/clear.1
+++ b/man/clear.1
@@ -1,5 +1,5 @@
 .\"***************************************************************************
 .\"***************************************************************************

-.\" Copyright 2018-2022,2023 Thomas E. Dickey                                *
+.\" Copyright 2018-2023,2024 Thomas E. Dickey                                *

 .\" Copyright 1998-2016,2017 Free Software Foundation, Inc.                  *
 .\"                                                                          *
 .\" Permission is hereby granted, free of charge, to any person obtaining a  *
 .\" Copyright 1998-2016,2017 Free Software Foundation, Inc.                  *
 .\"                                                                          *
 .\" Permission is hereby granted, free of charge, to any person obtaining a  *


@@ -27,139 +27,160 @@
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"

-.\" $Id: clear.1,v 1.29 2023/04/09 08:28:00 tom Exp $
-.TH @CLEAR@ 1 ""
-.\" these would be fallbacks for DS/DE,
-.\" but groff changed the meaning of the macros.
-.de NS
-.ie n  .sp
-.el    .sp .5
-.ie n  .in +4
-.el    .in +2
-.nf
-.ft C                  \" Courier
-..
-.de NE
-.fi
-.ft R
-.ie n  .in -4
-.el    .in -2
-..
-.ie \n(.g .ds `` \(lq
-.el       .ds `` ``
-.ie \n(.g .ds '' \(rq
-.el       .ds '' ''
+.\" $Id: clear.1,v 1.48 2024/03/16 15:35:01 tom Exp $
+.TH @CLEAR@ 1 2024-03-16 "ncurses @NCURSES_MAJOR@.@NCURSES_MINOR@" "User commands"
+.ie \n(.g \{\
+.ds `` \(lq
+.ds '' \(rq
+.ds '  \(aq
+.\}
+.el \{\
+.ie t .ds `` ``
+.el   .ds `` ""
+.ie t .ds '' ''
+.el   .ds '' ""
+.ie t .ds '  \(aq
+.el   .ds '  '
+.\}
+.

 .de bP
 .ie n  .IP \(bu 4
 .el    .IP \(bu 2
 ..
 .de bP
 .ie n  .IP \(bu 4
 .el    .IP \(bu 2
 ..

-.ds n 5
+.

 .SH NAME
 .SH NAME

-\fB@CLEAR@\fP \- clear the terminal screen
+\fB\%@CLEAR@\fP \-
+clear the terminal screen

 .SH SYNOPSIS
 .SH SYNOPSIS

-\fB@CLEAR@\fR [\fB\-T\fItype\fR] [\fB\-V\fR] [\fB\-x\fR]
-.br
+.B @CLEAR@
+.RB [ \-x ]
+.RB [ \-T\ \c
+.IR terminal-type ]
+.PP
+.B "@CLEAR@ \-V"

 .SH DESCRIPTION
 .SH DESCRIPTION

-\fB@CLEAR@\fP clears your terminal's screen if this is possible,
-including the terminal's scrollback buffer
-(if the extended \*(``E3\*('' capability is defined).
-\fB@CLEAR@\fP looks in the environment for the terminal type
-given by the environment variable \fBTERM\fP,
-and then in the
-\fBterminfo\fP database to determine how to clear the screen.
+\fB\%@CLEAR@\fP clears your terminal's screen and its scrollback buffer,
+if any.
+\fB\%@CLEAR@\fP retrieves the terminal type from the environment
+variable \fITERM\fP,
+then consults the \fIterminfo\fP terminal capability database entry for
+that type to determine how to perform these actions.

 .PP
 .PP

-\fB@CLEAR@\fP writes to the standard output.
-You can redirect the standard output to a file (which prevents
-\fB@CLEAR@\fP from actually clearing the screen),
-and later \fBcat\fP the file to the screen, clearing it at that point.
+The capabilities to clear the screen and scrollback buffer are named
+\*(``clear\*('' and \*(``E3\*('', respectively.
+The latter is a \fIuser-defined capability\fP,
+applying an extension mechanism introduced in \fI\%ncurses\fP 5.0
+(1999).

 .SH OPTIONS
 .SH OPTIONS

-.PP
-.TP 5
+\fB\%@CLEAR@\fP recognizes the following options.
+.TP 9 \" "-T type" + 2n

 .B \-T \fItype\fP
 .B \-T \fItype\fP

-indicates the \fItype\fP of terminal.
-Normally this option is
-unnecessary, because the default is taken from the environment
-variable \fBTERM\fP.
-If \fB\-T\fP is specified, then the shell
-variables \fBLINES\fP and \fBCOLUMNS\fP will also be ignored.
+produces instructions suitable for the terminal \fItype\fP.
+Normally,
+this option is unnecessary,
+because the terminal type is inferred from the environment variable
+\fITERM\fP.
+If this option is specified,
+\fB\%@CLEAR@\fP ignores the environment variables \fILINES\fP and
+\fI\%COLUMNS\fP as well.

 .TP
 .B \-V
 .TP
 .B \-V

-reports the version of ncurses which was used in this program, and exits.
-The options are as follows:
+reports the version of \fI\%ncurses\fP associated with this program and
+exits with a successful status.

 .TP
 .B \-x
 .TP
 .B \-x

-do not attempt to clear the terminal's scrollback buffer
-using the extended \*(``E3\*('' capability.
+prevents \fB\%@CLEAR@\fP from attempting to clear the scrollback buffer.
+.SH PORTABILITY
+Neither IEEE Std 1003.1/The Open Group Base Specifications Issue 7
+(POSIX.1-2008) nor X/Open Curses Issue 7 documents \fB\%@CLEAR@\fP.
+.PP
+The latter documents \fBtput\fP,
+which could be used to replace this utility either via a shell script or
+by an alias
+(such as a symbolic link)
+to run \fB\%@TPUT@\fP as \fB\%@CLEAR@\fP.

 .SH HISTORY
 .SH HISTORY

-A \fBclear\fP command appeared in 2.79BSD dated February 24, 1979.
-Later that was provided in Unix 8th edition (1985).
+A \fBclear\fP command using the \fItermcap\fP database and library
+appeared in 2BSD (1979).
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=2BSD/src/clear.c
+Eighth Edition Unix (1985) later included it.
+.PP
+The commercial Unix arm of AT&T adapted a different BSD program
+(\fBtset\fP) to make a new command,
+\fBtput\fP,
+and replaced the \fBclear\fP program with a shell script that called
+\*(``\fBtput clear\fP\*(''.

 .PP
 .PP

-AT&T adapted a different BSD program (\fBtset\fP) to make
-a new command (\fBtput\fP),
-and used this to replace the \fBclear\fP command with a shell script
-which calls \fBtput clear\fP, e.g.,
-.NS
-/usr/bin/tput ${1:+-T$1} clear 2> /dev/null
+.RS 4
+.EX
+/usr/bin/tput ${1:+\-T$1} clear 2> /dev/null

 exit
 exit

-.NE
+.EE
+.RE

 .PP
 In 1989, when Keith Bostic revised the BSD \fBtput\fP command
 .PP
 In 1989, when Keith Bostic revised the BSD \fBtput\fP command

-to make it similar to the AT&T \fBtput\fP,
-he added a shell script for the \fBclear\fP command:
-.NS
+to make it similar to AT&T's \fBtput\fP,
+he added a \fBclear\fP shell script as well.
+.\" https://minnie.tuhs.org/cgi-bin/utree.pl?file=Net2/usr/src/usr.bin/\
+.\"   tput/clear.sh
+.PP
+.RS 4
+.EX

 exec tput clear
 exec tput clear

-.NE
+.EE
+.RE

 .PP
 The remainder of the script in each case is a copyright notice.
 .PP
 .PP
 The remainder of the script in each case is a copyright notice.
 .PP

-The ncurses \fBclear\fP command began in 1995 by adapting the original
-BSD \fBclear\fP command (with terminfo, of course).
-.PP
-The \fBE3\fP extension came later:
+In 1995,
+\fI\%ncurses\fP's \fBclear\fP began by adapting BSD's original
+\fBclear\fP command to use \fIterminfo\fP.
+The \fBE3\fP extension came later.

 .bP
 .bP

-In June 1999, \fBxterm\fP provided an extension to the standard control
+In June 1999, \fIxterm\fP provided an extension to the standard control

 sequence for clearing the screen.
 Rather than clearing just the visible part of the screen using
 sequence for clearing the screen.
 Rather than clearing just the visible part of the screen using

-.NS
-printf '\\033[2J'
-.NE
+.RS 8
+.PP
+.EX
+printf \*'\e033[2J\*'
+.EE
+.RE

 .IP
 .IP

-one could clear the \fIscrollback\fP using
-.NS
-printf '\\033[\fB3\fPJ'
-.NE
+one could clear the scrollback buffer as well by using
+.RS 8
+.PP
+.EX
+printf \*'\e033[\fB3\fPJ\*'
+.EE
+.RE

 .IP
 .IP

-This is documented in \fIXTerm Control Sequences\fP as a feature originating
-with \fBxterm\fP.
+instead.
+\*(``XTerm Control Sequences\fP\*('' documents this feature as
+originating with \fIxterm\fP.

 .bP
 .bP

-A few other terminal developers adopted the feature, e.g., PuTTY in 2006.
+A few other terminal emulators adopted it,
+such as PuTTY in 2006.

 .bP
 In April 2011, a Red Hat developer submitted a patch to the Linux
 kernel, modifying its console driver to do the same thing.
 .bP
 In April 2011, a Red Hat developer submitted a patch to the Linux
 kernel, modifying its console driver to do the same thing.

-The Linux change, part of the 3.0 release, did not mention \fBxterm\fP,
-although it was cited in the Red Hat bug report (#683733)
-which led to the change.
+Documentation of this change,
+appearing in Linux 3.0,
+did not mention \fIxterm\fP,
+although that program was cited in the Red Hat bug report (#683733)
+motivating the feature.

 .bP
 .bP

-Again, a few other terminal developers adopted the feature.
-But the
-next relevant step was a change to the \fBclear\fP program in 2013
-to incorporate this extension.
+Subsequently,
+more terminal developers adopted the feature.
+The next relevant step was to change the \fI\%ncurses\fP \fBclear\fP
+program in 2013 to incorporate this extension.

 .bP
 .bP

-In 2013, the \fBE3\fP extension was overlooked in \fB@TPUT@\fP with
-the \*(``clear\*('' parameter.
-That was addressed in 2016 by reorganizing \fB@TPUT@\fP to share
-its logic with \fB@CLEAR@\fP and \fB@TSET@\fP.
-.SH PORTABILITY
-Neither IEEE Std 1003.1/The Open  Group  Base  Specifications  Issue  7
-(POSIX.1-2008) nor X/Open Curses Issue 7 documents @TSET@ or @RESET@.
-.PP
-The latter documents \fBtput\fP, which could be used to replace this utility
-either via a shell script or by an alias (such as a symbolic link) to
-run \fB@TPUT@\fP as \fB@CLEAR@\fP.
+In 2013,
+the \fBE3\fP capability was not exercised by
+\*(``\fB\%@TPUT@ clear\fP\*(''.
+That oversight was addressed in 2016 by reorganizing \fB\%@TPUT@\fP to
+share its logic with \fB\%@CLEAR@\fP and \fB\%@TSET@\fP.

 .SH SEE ALSO
 .SH SEE ALSO

-\fB@TPUT@\fP(1),
-\fBxterm\fP(1),
-\fBterminfo\fP(\*n).
-.PP
-This describes \fBncurses\fP
-version @NCURSES_MAJOR@.@NCURSES_MINOR@ (patch @NCURSES_PATCH@).
+\fB\%@TPUT@\fP(1),
+\fB\%xterm\fP(1),
+\fB\%terminfo\fP(5)