Pipe output and capture exit status in Bash

using bash's set -o pipefail is helpful

pipefail: the return value of a pipeline is the status of the last command to exit with a non-zero status, or zero if no command exited with a non-zero status

There is an internal Bash variable called $PIPESTATUS; it’s an array that holds the exit status of each command in your last foreground pipeline of commands.

<command> | tee out.txt ; test ${PIPESTATUS[0]} -eq 0

Or another alternative which also works with other shells (like zsh) would be to enable pipefail:

set -o pipefail
...

The first option does not work with zsh due to a little bit different syntax.

Dumb solution: Connecting them through a named pipe (mkfifo). Then the command can be run second.

 mkfifo pipe
 tee out.txt < pipe &
 command > pipe
 echo $?