Open3.popen3 returns wrong error Errno::ENOENT on Windows

Question

I have following piece of code in a test.rb file:

require 'open3'

cmd = 'C:\Program Files\foo\bar.exe'

Open3.popen3(cmd) do |stdin, stdout, stderr, wait_thr|

  puts "stdout: #{stdout.read}"

  puts "\n\n"

  puts "stderr: #{stderr.read}"

end

bar.exe

is a console application that I created, located in the

C:\Program Files\foo\

directory. It works like following:

When I run
foo.exe
it outputs
"Hello world!"

When I run
foo.exe
with any argument (eg.
foo.exe /blah
), it outputs a help message.

When I run

ruby test.rb

I am getting the following error:

C:\RailsInstaller/Ruby2.2.0/lib/ruby/2.2.0/open3.rb:193:in 'spawn': No such file or directory - C:\Program Files\foo\bar.exe (Errno::ENOENT)

from C:\RailsInstaller/Ruby2.2.0/lib/ruby/2.2.0/open3.rb:193:in 'popen_run'

from C:\RailsInstaller/Ruby2.2.0/lib/ruby/2.2.0/open3.rb:193:in 'popen3'

from test.rb:3:in '<main>'

If I change the code in test.rb to call the

popen3

method like this:

Open3.popen3(cmd, '')

, I don't get the

Errno::ENOENT

error, instead I am getting the help message. But I want the

"Hello World"

output.

This is a strange behavior. I have searched for a solution but nothing is working including this answer.
My question is why am I getting this error and how to solve it?

Answer 1

You are having trouble because "Program Files" is a folder with a space in it. Whenever that happens, you need to double quote it, just as you would on a cmd.exe prompt. And when you're double-quoting, you must remember that your backslash character "\" is an escape character, so you have to double-backslash to get the proper folder separators for Windows. I'm going to use code which actually returns something in my environment; adjust it to your taste. So your code should look like:

require 'open3'
cmd = "\"C:\\Program Files\\Git\\bin\\git.exe\""
Open3.popen3(cmd) do |stdin, stdout, stderr, wait_thr|
  puts "stdout: #{stdout.read}"
  puts "\n\n"
  puts "stderr: #{stderr.read}"
end

If you have command line parameters to pass to git, you'd do it like this:

require 'open3'
cmd = "\"C:\\Program Files\\Git\\bin\\git.exe\" --version"
Open3.popen3(cmd) do |stdin, stdout, stderr, wait_thr|
  puts "stdout: #{stdout.read}"
  puts "\n\n"
  puts "stderr: #{stderr.read}"
end

Open3.popen3 returns wrong error Errno::ENOENT on Windows

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