Shell out from ruby while setting an environment variable

Question

I need to shell out to a process while setting an environment variable for it. I tried this one-liner:

system "RBENV_VERSION=system ruby extconf.rb" 

This syntax works in shell script but not from ruby. (Update: turns out this syntax works from ruby after all, but I failed to see its effect due to my particular use-case.)

So I'm doing this:

rbenv_version = ENV['RBENV_VERSION'] ENV['RBENV_VERSION'] = 'system' begin   system "ruby extconf.rb" ensure   ENV['RBENV_VERSION'] = rbenv_version end 

I'm forced to such a long expression because I don't want to override the environment variable permanently if it already had a value.

Anything shorter that comes to your mind?

Answer 1

system({"MYVAR" => "42"}, "echo $MYVAR") 

system accepts any arguments that Process.spawn accepts.

Answer 2

Ruby 1.9 includes Process::spawn which allows an environ hash to be provided.

Process::spawn is also the foundation for system, exec, popen, etc.
You can pass an environment to each.

Under Ruby 1.8, you may want to consider the POSIX::Spawn library,
which provides the same interfaces