#!/bin/sh
#
# backslashify
# 
# AUTHOR:
#   Dan Harkless                                                    <opensource@
#   http://harkless.org/dan/software/                              harkless.org>
# 
# COPYRIGHT:
#   This file is Copyright (C) 1998 by Dan Harkless, and is released under the
#   GNU General Public License <http://www.gnu.org/copyleft/gpl.html>.
#
# USAGE:
#   % backslashify [-basic] [<arguments>]
#
# DESCRIPTION:
#   This filter puts backslashes in front of characters that are special to
#   commands that process regular expressions.  
#
#   By default, all extended regexp characters, [$()*+.?[\^|], are backslashed.
#   This is especially useful when you have a script that's 'egrep'ping for an
#   expression that includes a variable, the contents of which are unpredictable
#   and may include special characters (e.g. "c++filt.c").
#
#   On the other hand, if your script is using 'sed' on a variable, you only
#   want basic (not extended) regexp characters to be backslashed: [$*.[\^].
#   This is accomplished by using the -basic option.
#   
#   If you put anything else on the commandline, it will be backslashified.
#   Otherwise, stdin will be backslashified.
#
# DATE        MODIFICATION
# ==========  ==================================================================
# 1998-03-04  Added -basic for use with non-extended regexp commands like sed.
# 1997-06-04  Original.

basic_regexp=0

if [ "$1" = "-basic" ]; then
    basic_regexp=1
    shift
fi

if [ $# = 0 ]; then
    # Backslashify stdin.
    if [ $basic_regexp = 1 ]; then
	            sed 's/[$*.[\^]/\\&/g'
    else # extended regexp
	            sed 's/[$()*+.?[\^|]/\\&/g'
    fi
else
    # Backslashify arguments.
    if [ $basic_regexp = 1 ]; then
	echo "$*" | sed 's/[$*.[\^]/\\&/g'
    else # extended regexp
	echo "$*" | sed 's/[$()*+.?[\^|]/\\&/g'
    fi
fi