tee - read stdin and write to both stdout and files

Options you will use

-a, --append

Append to the files instead of overwriting.

Examples

$ echo 'x' | sudo tee /etc/sysctl.d/99-x.conf

the way to write a root-owned file

$ make 2>&1 | tee build.log

see the output AND keep it

Gotchas

• cmd | tee log makes $? the exit status of TEE, not cmd. Add set -o pipefail or check ${PIPESTATUS[0]}.