Sorting and columns

Putting lines in order

• sort arranges lines alphabetically (or, with -n, as numbers):

sort names.txt

• sort -r reverses the order; sort -n is for lists of numbers.

Removing duplicates

• uniq removes neighbouring repeated lines. Because it only looks at neighbours, you usually sort first:

sort names.txt | uniq

• Add uniq -c to also count how many times each line appeared.

Picking out columns

• Many files have columns separated by a character — a comma, a colon, a tab.
• cut pulls out the columns you want. -d sets the delimiter, -f the field:

cut -d : -f 1 people.txt

• That takes the first field of each name:age line — the names.

Common mistakes

• sort is alphabetical; sort -n sorts numbers correctly.
• cut needs the right delimiter with -d.