Bash script to find/replace a line in a file

replace-line.sh

#!/usr/bin/env bash

######################################################################################
# USAGE: bash bash/replace-line.sh "replace this line" "to this line" in-this-file.txt
######################################################################################

function escapeSlashes {
    sed 's/\//\\\//g'
}

# replace-line.sh directory
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"

# First argument (old value)
OLD_LINE_PATTERN=$1

# Second argument (new value)
NEW_LINE=$2

# Third argument (file to replace text)
FILE=$3

# New value escaped (values may contain slashes; escape them).
NEW_VALUE=$(echo "${NEW_LINE}" | escapeSlashes)

cat "$FILE" | sed -e 's/'"$OLD_LINE_PATTERN"'/'"$NEW_VALUE"'/' > $DIR/temp.txt
mv $DIR/temp.txt "${FILE}"