Description of the problem / feature request:

tools/test/test-setup.sh has a comment and layers of workarounds for running a dependent "ps"-like program to test if a process exists. It claims that its convoluted fallbacks is because it can't test directly, but I think it can.

What operating system are you running Bazel on?

OSX.

Darwin 21.2.0 i386

Proposal

The magic 'kill' signal-spec of "0" means to test that a PID still exists and could receive a signal, without actually sending it a signal.

'kill' syscall man page says, "The kill() function sends the signal specified by sig to pid, a process or a group of processes. Typically, Sig will be one of the signals specified in sigaction(2). A value of 0, however, will cause error checking to be performed (with no signal being sent). This can be used to check the validity of pid."

And since "kill" is often a shell built-in, this has almost no cost on the OS, unlike spinning up a new process for "ps".

So, instead of the

while ps -p $$ &> /dev/null || [ "`pgrep -a -g $$ 2> /dev/null`" != "" ]; do

, it could be just while kill -0 $PPID &>/dev/null; do

(Contributing doc says to report bugs first instead of just submitting a PR. I'll make a PR too, if no one objects.)