.\"	manual page for bsfilt(1)
.\"
.\"
.\"	Copyright (c) 1991 Purdue University Research Foundation,
.\"	West Lafayette, Indiana 47907.  All rights reserved.
.\"
.\"	Written by Victor A. Abell <abe@mace.cc.purdue.edu>,  Purdue
.\"	University Computing Center.  Not derived from licensed software;
.\"	derived from awf(1) by Henry Spencer of the University of Toronto.
.\"
.\"	Permission is granted to anyone to use this software for any
.\"	purpose on any computer system, and to alter it and redistribute
.\"	it freely, subject to the following restrictions:
.\"
.\"	1. The author is not responsible for any consequences of use of
.\"	   this software, even if they arise from flaws in it.
.\"
.\"	2. The origin of this software must not be misrepresented, either
.\"	   by explicit claim or by omission.  Credits must appear in the
.\"	   documentation.
.\"
.\"	3. Altered versions must be plainly marked as such, and must not
.\"	   be misrepresented as being the original software.  Credits must
.\"	   appear in the documentation.
.\"
.\"	4. This notice may not be removed or altered.
.\"
.TH BSFILT 1 "February, 1991"
.BY "Purdue University"
.SH NAME
bsfilt, colcrt \- a colcrt-like backspace filter
.SH SYNOPSIS
.B bsfilt
[
.B -
] [
.B -U
] [ file ... ]
.SH DESCRIPTION
.I Bsfilt
filters backspace sequences from the input \fIfile\fR(s)
(standard input if none)
in an approximation of
.IR colcrt (1).
Both the backspace and the character it returns to are removed,
unless they form an underline sequence.
Underline sequences are treated according to the settings of
the
.B \-
and
.B \-U
options.
.SH OPTIONS
.TP
.B \-
specifies that no underlining of any kind is to be propagated.
Without this option or the
.B \-U
option,
.I bsfilt
approximates underlining with minus signs (`-') in following lines.
.TP
.B \-U
specifies that underlining with underscore (`_') and backspace (`\b')
character sequences is permitted.
.SH SEE ALSO
cawf(1), colcrt(1) and nroff(1).
.SH DIAGNOSTICS
Diagnostic messages are delivered to the standard error file.
.SH HISTORY
Vic Abell of Purdue University wrote
.I bsfilt
to have a backspace filter for
.IR cawf (1)
that is independent of licensed source code.
.SH BUGS
The maximum length of a line that can be underlined with minus signs is
fixed.
.LP
.I Bsfilt
does not examine the characters that are being overprinted via backspace
operations.
Thus, overprinting that is intended to form a new character from several
different ones is ineffective and only the last character of the
sequence is propagated \- e. g., ``o^H+'', intended to look like
a bullet, is reduced to `+'.