Shell Scripts for Batch Renaming .sh Files and Monitoring Port 80 Requests

This guide presents two practical Bash scripts for Linux system administrators.

Task 1 – Rename and modify .sh files: The script searches the current directory (including sub‑directories) for files ending with .sh, renames each to .shell, and removes the second line of the renamed file.

#!/bin/bash
ALL_SH_FILE=$(find . -type f -name "*.sh")
for file in ${ALL_SH_FILE[*]}
do
    filename=$(echo $file | awk -F'.sh' '{print $1}')
    new_filename="${filename}.shell"
    mv "$file" "$new_filename"
    sed -i '2d' "$new_filename"
done

Task 2 – Monitor port 80 request volume: The script repeatedly obtains the request counts of the top‑20 IP addresses accessing port 80, checks whether the smallest count among them exceeds 500, and if so writes a system activity report to alert.txt; otherwise it waits 600 seconds before retrying.

#!/bin/bash
state="true"
while $state
do
    SMALL_REQUESTS=$(netstat -ant | awk -F'[ :]+' '/:22/{count[$4]++} END {for(ip in count) print count[ip]}' | sort -n | head -20 | head -1)
    if [ "$SMALL_REQUESTS" -gt 500 ]; then
        sar -A > alert.txt
        state="false"
    else
        sleep 600
        continue
    fi
done