Exporting an Environment Variable in Ruby

Question

How do I export an environment variable from within a Ruby script to the parent shell? For example, implementing a naïve implementation of the read Bash builtin

Answer 1

I just tried this and it looks good.

cmd = "echo \"FOO is \\\"$FOO\\\"\"";                                
system(cmd);

# Run some Ruby code (same program) in the child process
fork do
    puts "In child process. parent pid is #$$"
    ENV['FOO']='foo in sub process';
    system(cmd);
    exit 99
end
child_pid = Process.wait
puts "Child (pid #{child_pid}) terminated with status #{$?.exitstatus}"

system(cmd);

This seems to work well - at least on MacOSX

I get

FOO is ""
In child process. parent pid is 1388
FOO is "foo in sub process"
Child (pid 1388) terminated with status 99
FOO is ""

Seems nice in it restores prior state automatically

Ok - now tried a different one as this doesn't spawn 2 subprocesses

Use Process.spawn(env,command)

pid = Process.spawn({ 'FOO'=>'foo in spawned process'}, cmd );
pid = Process.wait();  

This acts like the C system call and allows you to specify pipes and all that other stuff too.