[ Bash Scripting ]



Simple Bash Scripting Cheatsheet


Nano Shortcuts
ctrl v                  Next page.
ctrl y                  Previous page.
ctrl w                  Where is (find).
ctrl k                  Cut that line of test.
ctrl x                  Exit editor.

Create a text file:
touch file              Creates an empty file.
ifconfig > tmp  pipe the output of a command
nano file

Create a file and append text to it:
ifconfig > tmp     
echo >> tmp
ping google.com -c3 >> tmp

How to view a file:
cat file                Show entire contents of file.
more file               Show one page at a time.  Space bar for next page and (q) to exit.
head file               Show the first 10 lines.
head -15 file   Show the first 15 lines.
tail file               Show the last 10 lines.
tail -15 file   Show the last 15 lines.
tail -f file    Useful when viewing the output of a log file.

pipe
cat tmp | grep Bcast    Feeds the output of one process to the input of another process.

Processes
ps aux                  Show all running process for all users.
kill -9 PID             Nicely kill a PID.

Word Count
wc -l tmp2              Count the number of lines in a file

cut
-d  delimiter
-f  fields

sort
Sort by unique          sort -u file
sort IP addresses correct               sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n
cat tmp2 | cut -d '(' -f2 | cut -d ')' -f1 | sort -u            Isolate the IP address

awk
awk '{print $1}' file           Show the 1st column.
awk '{print $1,$5}' file        Show the 1st and 5th columns.

[+] grep
grep -v         Remove a single string.
grep -v 'red' file

[+] egrep -v
Remove multiple strings egrep -v '(red|white|blue)' file

sed
sed 's/FOO/BAR/g' file          Replace FOO with BAR.
sed 's/FOO//g' file             Replace FOO with nothing.
sed '/^FOO/d' file                      Remove lines that start with FOO.

colour
31=red 32=green 33=yellow 34=blue 35=magenta 36=cyan 
echo -e "\e[1;34mThis is a blue text.\e[0m"




Bash Scripts
------------

Simple bash script:
#!/bin/bash
clear
echo
echo
print "Hello world."

Make a file executable.
chmod +x file
chmod 755 file

Variables
name=Bob
echo $name
user=$(whoami)
echo $user
echo 'Hello' $name. 'You are running as' $user.

#!/bin/bash
clear
echo "Hello World"
name=Bob
ip=`ifconfig | grep "Bcast:" | cut -d":" -f2 | cut -d" " -f1`
echo "Hello" $name "Your IP address is:" $ip

User Input
read -p "Domain: " domain

#!/bin/bash
echo "Please input your domain:"
read -p "Domain:" domain
ping -c 5 $domain

Check For No User Input
if [ -z $domain ]; then
        echo
        echo "#########################"
        echo
        echo "Invalid choice."
        echo
        exit
fi

For loops
#!/bin/bash

for host in $(cat hosts.txt)
do
        command $host
done

One Liners

Port Scan:
for port in $(cat Ports.txt); do nc -nzv 192.168.0.1 $port & sleep 0.5; done