:
##########################################################################
# Title      :	chtext - change text in multiple files
# Author     :	Heiner Steven <heiner.steven@odn.de>
# Date       :	1993-05-13
# Requires   :	
# Category   :	Text Utilities
# SCCS-Id.   :	@(#) chtext	1.6 04/07/08
##########################################################################
# Description
#    -	This script basically does the following:
#	    sed 's/old/new/g' < IN > TMP && mv TMP IN
#
# Caveats
#    o	Should have an option to enable the special meaning of "&"
#	in the "sed" expression (suggested by Douglas Kramer)
##########################################################################

PN=`basename "$0"`			# Program name
VER='1.6'

usage () {
    echo >&2 "$PN - change text in multiple files, $VER
Heiner Steven 1993-2004; Public Domain

usage: $PN [-fq] [-s searchpat] [-n newtext] file [...]
    -s:  search expression that should be replaced
    -n:  new text
    -f:  remove (instead replace) search expression
    -q:  quiet mode

If the search pattern or the new text is not specified
on the commandline, $PN will prompt for it."
    exit 1
}

msg () {
    [ "$Quiet" = true ] && return 0
    echo >&2 "$PN:" "$@"
}

# GetStr (prompt, varname)
# Note: "call by name", varname is the name of a variable, not a value:
#	Example: file=test.txt; GetStr "file name" file

GetStr () {
    test $# -eq 2 || return 1

    answer=
    echo "$1: \c"		# some UNIXes need "echo -n"
    read answer || { echo; exit 1; }

    eval $2=\$answer		# assign new value to variable
    return 0
}

Tmp="cht$$"				# Temporary file
OldText=				# Search pattern
NewText=				# New Text
Interactive=true				# Parameter -f
Quiet=false				# Parameter -q

while [ $# -gt 0 ]
do
    case "$1" in
	-s)	OldText="$2"
		shift ;;
	-n)	[ $# -gt 1 ] && Interactive=false
		NewText="$2"
		shift ;;
	-f)	Interactive=false ;;
	-q)	Quiet=true ;;
	--)	shift; break ;;			# Files will follow
	-*)	usage ;;
	*)	break ;;			# File name(s)
    esac
    shift
done

[ $# -lt 1 ] && usage

if [ -z "$OldText" ] || [ -z "$NewText" ]
then
    if [ "$Quiet" != true ]
    then
	echo >&2 "$PN - change text, $VER"
	echo >&2
	msg "Files to change:" "$@"
    fi

    if [ -z "$OldText" ]
    then
	GetStr "old text" OldText
	[ -z "$OldText" ] && exit 1
    fi

    if [ -z "$NewText" ] && [ "$Interactive" = true ]
    then
	GetStr "new text" NewText
	if [ -z "$NewText" ]
	then
	    echo >&2 "$PN: Really remove '$OldText' (y/n)? \c"
	    read answer || exit 1
	    case  "$answer" in
		y|true)	break ;;
		*)	exit 1 ;;
	    esac
	fi
    fi
fi

if [ "$OldText" = "$NewText" ]
then
    echo >&2 "$PN: old and new text are identical - no substitution necessary!"
    exit 1
fi

case "$OldText$NewText" in
    *
*)
    	echo >&2 "
$PN: ERROR: text to change cannot contain an ^A (ASCII 1) character,
because it is used internally as a delimiting character"
	exit 1
esac

msg "change '$OldText' to '$NewText'"

# We are using NewText on the right side of an "sed" expression, and
# therefore have to protect the special character '&' from being
# interpreted as meaning "the matching text":

NewText=`sed 's/&/\\\\&/g' <<EOT
$NewText
EOT
`
errors=0
for file
do
    [ -f "$file" -a -r "$file" -a -w "$file" ] || {
	echo >&2 "$PN: ERROR: no permisson to change '$file' - ignored"
	errors=`expr $errors + 1`
	continue
    }

    msg "$file"

    cp -p "$file" "$Tmp" || {
    	echo >&2 "$PN: ERROR: could not create temporary file for '$file'"
	errors=`expr $errors + 1`
	continue
    }

    sed -e 's
'"$OldText"'
'"$NewText"'
g' < "$file" > "$Tmp" || {
	echo >&2 "$PN: ERROR: could not change '$file'"
	errors=`expr $errors + 1`
	continue
    }

    if cmp "$file" "$Tmp" >/dev/null
    then
    	msg "INFO: file has not changed: $file"
	rm -f "$Tmp" >/dev/null 2>&1
	continue
    fi

    mv "$Tmp" "$file" || {
	echo >&2 "$PN: ERROR: could not rename '$Tmp' to '$file' - file not changed!"
	errors=`expr $errors + 1`
	continue
    }
done

if [ $errors -ne 0 ]
then
    exit 1
fi
exit 0