tee and exit status

Question

Is there an alternative to tee which captures standard output and standard error of the command being executed and exits with the same exit status as the processed command?

Something like the following:

eet -a some.log -- mycommand --foo --bar

Where "eet" is an imaginary alternative to "tee" :) (-a means append and -- separates the captured command). It shouldn't be hard to hack such a command, but maybe it already exists and I'm not aware of it?

Answer 1

This works with Bash:

(
  set -o pipefail
  mycommand --foo --bar | tee some.log
)

The parentheses are there to limit the effect of pipefail to just the one command.

From the bash(1) man page:

The return status of a pipeline is the exit status of the last command, unless the pipefail option is enabled. If pipefail is enabled, the pipeline's return status is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands exit successfully.

Answer 2

I stumbled upon a couple of interesting solutions at Capture Exit Code Using Pipe & Tee.

1. There is the $PIPESTATUS variable available in Bash:

   false | tee /dev/null
   [ $PIPESTATUS -eq 0 ] || exit $PIPESTATUS
   

2. And the simplest prototype of "eet" in Perl may look as follows:

   open MAKE, "command 2>&1 |" or die;
   open (LOGFILE, ">>some.log") or die;
   while (<MAKE>) { 
       print LOGFILE $_; 
       print 
   }
   close MAKE; # To get $?
   my $exit = $? >> 8;
   close LOGFILE;