How do I change file permissions?

Use chmod, e.g. chmod 755 file or chmod +x script.sh. chown changes the owner of a file.

find . -name '*.txt' searches by name; use grep -r 'text' . to search file contents recursively.

How do I see running processes?

ps aux lists processes, top or htop shows them live, and kill stops one.

cat shows the whole file, less paginates it, and head/tail show the first or last lines (tail -f follows a log).

It sends the output of one command as the input to the next, e.g. cat file | grep error | wc -l.

Reference

Essential Unix/Linux commands for everyday shell work. Click any card to copy.