7 Useful macOS/Linux Commands

1. wc

Counting lines, words, and characters respectively. Character counting includes invisible chars.

Useful Flags

• -l: count lines only.

• -w: count words only.

• -c: count characters only.

2. ls

Listing files and directories. ls automatically prints its output as a single column when its output is redirected.

e.g. to count the number of files in a directory:

ls | wc -l

Useful Flags

• -l: print output in a single column. This will also include other file attributes per file in the output.

• -C: print output in multiple columns. Pay attention – this flag name is uppercase!

• -a: include hidden files.

3. head

Peeking at the top of a file. Can be used to truncate long output from other commands.

e.g. list the first five files in a directory:

ls | head -n5

Useful Flags

• -n: specify how many lines to print. Defaults to 10.

4. cut

Prints specific columns from a text file.

Useful Flags

• -f: the number of columns to print. This flag can accept a comma-separated string to print specific columns, -f1,3, or a dash-separated range, e.g. -f2-4.

• -d: specify the delimiter character, which is \t by default.

• -c: defines the character position of what constitutes a column. This flag can accept a comma-separated string to print specific columns or a dash-separated range.

5. grep

Finds patterns in files.

Useful Flags

• -v: find matches that don’t contain this argument.

• -w: match full words only, not parts of words.

6. sort

Reorders the lines in a file (ascending order by default).

Useful Flags

• -r: order in descending order.

7. uniq

Detects repeated adjacent lines in a file and removes the duplicates.

Useful Flags

• -c: count occurrences.

8. sha256sum

I know the title said 7 commands but here’s an extra one on the house – outputs the SHA-256 checksum of a file.

Useful Flags

• -b: treat the input as binary.