ls

To display a human-readable file size in long format using ls:

$ ls -lh <file>

To display the size of files in a directory:

$ ls -lh <directory>

sort

To sort by size in descending order:

$ ls -lhS <directory>

To sort by size in ascending order:

$ ls -lhrS <directory>

du

To get the size of a directory, use the du command:

$ du -sh <directory>