Question

Ubuntu 12.04

Sinatra 1.3.3

Why does passing an argument to a ruby system call (%x[] or “) give me a ‘not found’ error in my sinatra app? The same code works fine in a normal ruby script running from the same directory.

I have a file test.rb like this

output = %x["ls"] 
p output

When I run it with “ruby test.rb” I get the contents of the current directory in the console, as expected.

If I modify the program to give an argument to the system call like so:

output = %x["ls sub_dir/"] 
p output

I get the contents of sub_dir, which sits in the current directory, as expected.

So far so good.

Now if I make a Sintra app with a post method:

require 'rubygems'
require 'bundler/setup'
require 'sinatra'

post "/" do
 output = x["ls"]
 return output
end

The response to a Post call to “/” returns the contents of the current directory, which includes ‘sub_dir’, as expected.

If I try to add the argument to the system call to the sinatra app like so:

require 'rubygems'
require 'bundler/setup'
require 'sinatra'

post "/" do
 output = x["ls sub_dir/"]
 return output
end

the response is nil and there is an error in the console:

sh: 1: ls sub_dir/: not found

Why does adding a parameter to a system call in my sinatra app cause it to crash, when the same code called from a plain ruby script, run from the same location works perfectly.

By the way, the ‘ls’ example shown here is not the command I really need to run, so please don’t explain a different way to get this information. I have an executable file that takes a file name as a parameter that I need to run, which behaves exactly the same way.

Thanks in advance!

Answer 1

I rewrote the sinatra app in another file in the same directory.

Everything works as expected.

I did not find the reason and I deleted the original file so that I won’t lose anymore time trying to figure it out.