Basic examples of Bash Scripting

Goal Ping Sweep a range, generate a list of hosts that respond to ICMP Echo request with a reply

Format: Explanation of command + arguments

ping on a count (-c) of 1

Grep = show only quoted string

Cutting a delimiter (-d) specified in " " - in this case space

The field specifies the word (in this case the IP address so the flag yields a list of live hosts) of 4.

A range can be specified if 4-9 format is used

Sed is used to remove characters from final output 's/.$//' ***Research pending on the syntax of "sed" linux command ***

Example Command

ping -c 1 192.168.1.1 | grep "64 bytes from" | cut -d " " -f 4 | sed 's/.$//'

For loop - don't forget to add "; done" at the end so we don't run into '>' prompt issue

Below for loop: pings 1-255 hosts in 192.168.1.0/24

Grep prints the matching lines "64 bytes from"

Cut - remove sections from each #line of files using "-d".

--delimiter=DELIM - use delimiter instead of TAB for field delimiter. (in this case a space " ")

Sed - stream editor for filtering and transforming text helps us (more research needed on 's/.$//')

for i in {1..255}; do ping -c 1 192.168.1.$i | grep "64 bytes from" | cut -d " " -f 4 | sed 's/.$//'; done

My Traceroute - mtr

-r for outputing the results on the terminal

--no-dns does not resolve hostnames

sudo mtr -r -c 5 100.65.150.160 --no-dns | grep "." | cut -d " " -f 4

My traceroute and PING test - && executes command to the right of && after command to the left of && has been completed

In this case, mtr is executed, once it finishes for loop is executed

sudo mtr -r -c 5 192.168.1.1 && sudo mtr -r -c 5 192.168.1.18 && for i in {1..254}; do ping -c 5 192.168.1.$i | grep '1'; done

For loop + mtr - For i in range 160-190 runs a mytraceroute to specified #X.X.X.$i IP address (no DNS resolution flag)

Grep prints #the lines that #contain a "." (such as #ones with dotted decimal IP addresses)

Cut -d uses #space as delimiter ; done completes the #loop.

Useful for checking routing path in a whole subnet in dual homed networks with different egress and ingress paths

for i in {160..190}; do sudo mtr -r -c 5 100.65.150.$i --no-dns | grep "." | cut -d " " -f 4; done

But... How to save test results to a file? Add > after command followed by the filename (thanks to @nin)

ping -c 1 192.168.1.1 > ping.txt 

Use the ping command to obtain the IP address of the specified website

ping -c 1 google.com | grep from | cut -d " " -f 4 
~> 220.181.57.216