Question

Use HEAD to output the first 10 lines of ‘foo.txt’
Use CAT and pipe the output to HEAD to print out the first 10 lines of ‘foo.txt’
Use TAIL to print out the last 10 lines of ‘foo.txt’
Use HEAD to print out the first 3 lines of ‘foo.txt’
Use CAT and SORT to output ‘foo.txt’ in sorted order.
Use SORT (only) to output ‘foo.txt’ in sorted order.
Use SORT and pipe to UNIQ to output only the unique entries in sorted order in ‘foo.txt’.

Answer 1

1. head -n 10 foo.txt
first 10 lines of 'foo.txt' are displayed
2. cat foo.txt | head -n 10
initially foo.txt is read and then this is piped to the head command which retrieves the first 10 lines and displays them
3. tail -n 10 foo.txt
last 10 lines are displayed
4. head -n 3 foo.txt
first 3 lines are displayed
5. cat foo.txt | sort
initially foo.txt is read and then the lines are displayed in sorted order
6. sort foo.txt
displays file contents in sorted order
7. sort foo.txt | UNIQ
sorts the the file and then displays the unique lines in it.