Redirection

Two output streams

Every process has stdout (normal output) and stderr (error output), plus stdin for input. Redirection lets you send these to files instead of the screen.

>, >> and 2>

> overwrites a file with stdout, >> appends, 2> captures stderr separately.

ls /etc > listing.txt        # overwrite
ls /etc >> listing.txt       # append
ls /nope 2> errors.txt       # stderr only

Output:

cat errors.txt
# ls: cannot access '/nope': No such file or directory

Discard output

/dev/null is a black hole — redirect unwanted output there: command > /dev/null 2>&1 silences everything.