Process

I used to have some experience with basic shell command before, therefore this exercise was not hard for me to get start with. It gave me a chance to refresh my knowledge about shell command as well. I also found the website http://www.thegeekstuff.com/2010/11/50-linux-commands/ very useful for shell command beginners and learned a lot from it.

Exercise

C1

The command sort -n compare according to string numerical value, rather than character by character.

C2

wc -l < mydata.dat：wc -l doesn't have any command line parameters, it reads from standard input and send the contents of mydata.dat to wc's standard input. wc -l mydata.dat: wc gets a command line parameter telling it to open mydata.dat and get the output result.

C3

uniq is faster when working with large data sets, it removes only adjacent duplicated lines by comparing line by line. We can also use sort salmon.txt| uniq to remove all duplicated lines.

C4

we use "head -5" to get the first 5 lines of the animals.txt:

2012-11-05,deer
2012-11-05,rabbit
2012-11-05,raccoon
2012-11-06,rabbit
2012-11-06,deer

Then use "tail -3" to get the last three lines of previous output.

2012-11-05,raccoon                                                                                                                                                                 
2012-11-06,rabbit                                                                                                                                                                  
2012-11-06,deer

"sort -r > final.txt" sort the previous outcome and save the result as "final.txt".

2012-11-06,rabbit
2012-11-06,deer
2012-11-05,raccoon

C5

cut -d, -f 2 animals.txt | sort | uniq