#!/bin/bash
usage() {
echo "Usage: $(basename "$0") <REGEX> <STRING> <FILE>"
}
if [[ $# -ne 3 ]]; then
usage
exit 2
fi
REGEX=$1
STRING=$2
FILE=$3
if ! grep -q "$REGEX" "$FILE"; then
echo "$STRING" >>$FILE
echo appended
else
sed -i "s|$REGEX|$STRING|g" $FILE
echo replaced