Replace section in a file

replace-section-in-file.bash

#!/usr/bin/env bash

file_with_anchor_text=$1
file_with_new_content=$2

BEGIN_TEXT='<!-- BEGIN anchor text --!>'
END_TEXT='<!-- END anchor text --!>'

function get_line_number() {
    local text=$1
    echo $(grep -n "$text" $file_with_anchor_text | sed 's/\(.*\):.*/\1/g')
}

BEGIN_LINE=$(get_line_number "$BEGIN_TEXT")
END_LINE=$(get_line_number "$END_TEXT")

## Get the head and tail from $file_with_anchor_text and put the content form $file_with_new_content in between head and tail
cat <(head -n $(expr $BEGIN_LINE + 1) $file_with_anchor_text) $file_with_new_content <(tail -n +$(expr $END_LINE - 1) $file_with_anchor_text) >temp
mv temp $file_with_anchor_text