Editing Scripting Basics (section)

==== Bash ====

This script scans a given subnet for live hosts by sending ICMP echo requests (ping) and prints responding IP addresses.

<syntaxhighlight lang="bash">
#!/bin/bash

# Loop through IP addresses 1 to 254 in a subnet
for ip in $(seq 1 254); do

    # Send 1 ping (-c 1) to each IP in the given subnet (passed as $1)
    # Example: if $1 = 192.168.1, it pings 192.168.1.1 to 192.168.1.254
    ping -c 1 $1.$ip |

    # Look for lines in the ping output that contain "64 bytes"
    grep "64 bytes" |

    # Extract the 4th field (which contains the IP with a colon at the end)
    cut -d " " -f 4 |

    # Remove the trailing colon from the IP
    tr -d ":" &

done

# Notes:
# - $(...) is used instead of backticks \`...\` (modern syntax)
# - '&' runs each ping in the background for speed
# - This script prints a list of live hosts in the subnet
# - Usage: ./script.sh 192.168.1
</syntaxhighlight>

This script performs a fast parallel ping sweep across a /24 subnet and logs all responsive IPs to a CSV file.

<syntaxhighlight lang="bash">
# Scan a subnet (10.10.10.1–254) and log live hosts to a CSV file

# Loop over all IPs in the subnet
for ip in 10.10.10.{1..254}; do

  # Ping each IP once (-c1), wait max 1 second for reply (-W1)
  # Suppress output (&>/dev/null), and if host responds, log to file
  ping -c1 -W1 $ip &>/dev/null && echo "$ip,up" >> live.csv &

done

# Wait for all background pings to finish
wait
</syntaxhighlight>