This should be rebased against master.

If I'm reading right, these are launching a subshell to check the java executable, yes? Can't we just check if it is a normal executable file more cheaply?

If java must get launched I think we entertain java -Xinternalversion, This would not only test validity but could also be used for proper version handling. This is only 0.004s on my machine (I guess MacOS is higher).

If I'm reading right, these are launching a subshell to check the java executable, yes?

It is launching a subshell but it was always doing that because it's necessary to capture the output of command -v (which is a pure-shell alternative to which). It's not actually running any external programs, it's just checking that there's a file called java in $PATH that's executable. We could check that it succeeds before running it in a subshell but I don't think it's really necessary to save one fork on a code path that's going to error anyway.

@mrnoname1000 Ok that seems find then. We can merge this once you rebase it on master.

We can merge this, as it is a good change, but it doesn't actually fix jruby/jruby-launcher#44. That issue is actually about the native launcher, not the shell script.