upe(5.5): Replacing a file: overwrite

# overwrite: copy standard input to output after EOF
# final version

opath=$PATH
PATH=/bin:/usr/bin

case $# in
0|1) echo 'Usage: overwrite file cmd [args]' 1 >&2; exit 2
esac

file=$1; shift
new=/tmp/overwr1.$$; old=/tmp/overwr2.$$
trap `rm -f $new $old; exit 1` 1 2 15  # clean up files

if PATH=$opath "$@" >$new   # collect input
then

    cp $file $old    #save original file
    trap '' 1 2 15   # we are committed; ignore signals
    cp $new $file
else
    echo "overwirte: $1 tailed, $file unchanged" 1 >&2
    exit 1
fi
rm -f $new $old
# replace: replace str1 in ifles with str2, in place

PATH=/bin:/usr/bin

case $# in
0|1|2) echo 'Usage: replace str1 str2 files' 1 >&2; exit 1
esac

left="$1"; right="$2"; shift; shift

for i
do
    ./overwrite $i sed "s@$left@$right@g" $i
done