The-Unix-Shell-Teaching-Notes

4.7 Which Pipe?

The file animals.txt contains 8 lines of data formatted as follows:

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

The uniq command has a -c option which gives a count of the number of times a line occurs in its input. Assuming your current directory is shell-lesson-data/data/, what command would you use to produce a table that shows the total count of each type of animal in the file?

1. sort animals.txt | uniq -c
2. sort -t, -k2,2 animals.txt | uniq -c
3. cut -d, -f 2 animals.txt | uniq -c
4. cut -d, -f 2 animals.txt | sort | uniq -c
5. cut -d, -f 2 animals.txt | sort | uniq -c | wc -l

Solution

Option 4. is the correct answer. If you have difficulty understanding why, try running the commands, or sub-sections of the pipelines (make sure you are in the shell-lesson-data/data directory).

Episode 4 Exercise 8