How can I look at the start of a file?

The first thing most data scientists do when given a new dataset to analyze is figure out what fields it contains and what values those fields have. If the dataset has been exported from a database or spreadsheet, it will often be stored as comma-separated values (CSV). A quick way to figure out what it contains is to look at the first few rows.

We can do this in the shell using a command called head. As its name suggests, it prints the first few lines of a file (where "a few" means 10), so the command:

head seasonal/summer.csv

displays:

Date,Tooth
2017-01-11,canine
2017-01-18,wisdom
2017-01-21,bicuspid
2017-02-02,molar
2017-02-27,wisdom
2017-02-27,wisdom
2017-03-07,bicuspid
2017-03-15,wisdom
2017-03-20,canine

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What does head do if there aren't 10 lines in the file? (To find out, use it to look at the top of people/agarwal.txt.)