CMD Challenge
Solve shell tasks in the browser, each with a single command
CMD Challenge gives you a terminal in the browser and a list of tasks. Each task asks you to do something with a single shell command, such as print the last lines of a file, find files that contain a string, count lines with tabs, or split text on a character. Your command runs in a real bash shell inside a container, and the site checks the output.
Free · No login · Browser · Intermediate
About CMD Challenge
The tasks start with printing hello world and get harder. They train everyday command-line tools such as grep, find and sort. Two extra sets add more: in oops your bin directory is deleted, and 12 days has holiday puzzles.
It is free and needs no account. You can view other players' solutions. John Jarvis made it, and the code is on GitLab under the MIT license.
On Breakpoint since 23 Oct 2026.