Process

For this exercise, I created new files (eg salmon.txt and animals.txt) within my pipes directory. I got my hands dirty and played around in the command line, using a lot of "man uniq," "man cut" and "man sort." For Exercise #4, in particular, I tried to work it out logically in my head first, and then test to see if I had 'gotten' the logic (I did, hurray!) I found this helpful, because it allowed me to understand the commands both theoretically and practically (why they work vs how to make them work)

Exercises

1.) Using sort -n tells the computer to treat the list in question as numeric values, rather than strings. For example, "19" comes before "2" when we look at these values as strings ("1", the first character of "19" comes before "2", even if "2" is the single digit... it is effectively a string "20"). By using -n, 19 comes after 2 because it is numerically of greater value.

2.) The difference here is that in wc -l < mydata.dat, mydata.dat becomes the standard input for the command wc -l. wc -l reads the file from its standard input. If we just write wc -l mydata.dat, we have given wc -l a command line parameter.

3.) It is faster, when working with large data sets, to only compare line by line. You can remove all duplicates by sorting first, then using the uniq command. eg sort salmon.txt | uniq

4.) cat animals.txt passes the list of dates and animals

head -5 takes the first 5, ("2012-11-05, deer" thru "2012-11-06,deer")

tail -3 takes the last three of those 5 ("2012-11-05,raccoon" thru "2012-11-06,deer")

sort -r returns those 3 in reverse order ("2012-11-06,rabbit" "2012-11-06,deer" "2012-11-05,raccoon")

> final.txt stores that list in a text file called final.txt.

5.) The desired result (all animals printed, no duplicates) may be obtained by cut -d, -f 2 animals.txt | sort | uniq (See question 3, above)