Question

In trying to learn about Ruby execution methods, I found this blog post on five ways to run commands in Ruby http://mentalized.net/journal/2010/03/08/5_ways_to_run_commands_from_ruby/

The author creates a file err.rb, which outputs two lines, one on STDOUT, the other on STDERR

#!/usr/bin/env ruby
puts "out"
STDERR.puts "error"

The first way he tries to run it is with Kernal#` (backticks)

 >> `./err.rb`

      err
=> "out\n"

The point this illustrates is that when run with backticks

STDERR is output, but not captured
STDOUT is captured

When I tried to duplicate this on my system, I got a permission error

localhost:sites mike$ `./err.rb`
-bash: ./err.rb: Permission denied

I tried sudo ./err.rb with no change.

I can run ruby err.rb but that produces a different result than what the author got. Namely by running ruby err.rb I get

  out
  error

Can someone explain why I’m getting a permission error trying to run it with backticks, and also generally what the whole purpose of running it with backticks is.

Answer 1

Try add permission to execute, use “chmod +x that_file_name”
to execute using format “./file” the ‘file’ need to have execute permission

It runs when you ruby because ruby has execute permission and it simply read that file.

Try this

localhost:sites mike$ chmod +x err.rb