fourthLabNotes.txt

Quantification:
- Times of prev exp
- ?(0 or 1), *(0 or more), +(1 or more)
- aab?b: aabb or aab are valis (0 b's or 1 b)

sed: $sed 's/unix/linux/2
- Use the /1, /2 etc flags to replace the first, second occurrence of a pattern in a line. The below command replaces the second occurrence of the word “unix” with “linux” in a line
sed: $sed 's/unix/linux/'
- Sed command is mostly used to replace the text in a file. The below simple sed command replaces the word “unix” with “linux” in the file.

Getting subdirectories in a directory:
- ls -l | grep ^d (^ matches anything with the following char/word)
- | is the pipeline

grep matches lines
- echo "To be or not to be" | grep ".*be$"
	- output: to be or not to be
- echo "To be or \nnot to be" | grep ".*be$"
	- output: not to be
- echo "To be or \nnot to be" | grep "T.*e$"
	- Nothing