Ref: https://www.geeksforgeeks.org/sed-command-in-linux-unix-with-examples/
sed 's/unix/linux/' test.txt # Replacing or substituting string (sed command replaces the first occurrence of the pattern in each line and it)
sed 's/unix/linux/2' test.txt # Replacing the nth occurrence of a pattern in a line
sed 's/unix/linux/g' test.txt # Replace all occurances in a line as well
sed 's/unix/linux/3g' test.txt # Replace nth till last (3rd, 4th, 5th etc.,)
echo "Welcome To The Geek Stuff" | sed 's/\(\b[A-Z]\)/\(\1\)/g'
sed '3 s/unix/linux/' test.txt # restrict the sed command to replace the string on a specific line number.
sed 's/unix/linux/p' test.txt # The /p print flag prints the replaced line twice on the terminal. If a line does not have the search pattern and is not replaced, then the /p prints that line only once.
sed -n 's/unix/linux/p' test.txt # print only replaced lines, n option suppresses the duplicate rows generated by the /p flag and prints the replaced lines only one time.
sed '1,3 s/unix/linux/' test.txt # Replace range of lines
sed '5d' test1.txt # delete 5th line
sed '$d' test1.txt # delete last line
sed '3,6d' test1.txt # delete from range x to y
sed '12,$d' test1.txt # delete from nth line till last
sed '/abc/d' test1.txt # delete line which matches pattern
