Check disk space and memory in Bash

When a machine feels full, you need three numbers: how much disk is left, how large this folder is, and how much RAM is free. df, du, and free answer those questions. The -h and -m flags turn raw blocks into sizes people can read.

df reports filesystems. -h prints sizes in G and M instead of 1K blocks.

Readable disk usage:

du walks the current directory. -s prints one summary line. -h keeps the size readable. Together they are du -sh (or du -hs).

du -sh

Typical output: 128M . — this folder and everything under it.

free -m shows memory in megabytes: total, used, free, and available. Look at the available column when you want to know if a new process will fit.

Use df -h for the whole disk, du -sh for “why is this project huge?”, and free -m when programs start swapping.