Unexpected behavior when calling a Ruby script via PHP's shell_exec()

Question

I have a Ruby script that's being used to do some API calls/screen scraping, but our main app is in PHP. Our PHP app is using shell_exec() to call the Ruby script.

The ruby script works great when called from the command line–but it will randomly exits early when called via PHP's shell exec.

Here's an example of the Ruby script:

#!/usr/bin/env ruby
require 'rubygems'
require 'mysql'
require 'net/http'
require 'open-uri'
require 'uri'
require 'cgi'
require 'fileutils'

# Bunch of code here ... works fine 
somePath = 'http://foo.com/bar.php'
# Seems to always exit when I do a Net::HTTP or open-uri call 
post = Net::HTTP.post_form(URI.parse(somePath),{'id'=>ID,'q'=>'some query'})
data = post.body
# OR 
data = open(somePath).read
# More code here ... 

So, all I can deduce so far is that it's always exiting when I try to grab/read an external URL via net/http or open-uri calls. The pages I'm grabbing can accept POST or GET requests, but it seems to be exiting either way.

I'm outputting the results with PHP after the shell_exec call, but there are no error messages or exits. I do have messages being output by my Ruby script with "puts ...." here and there. Could that be a problem (I'm thinking 'no' because it doesn't exit with earlier puts messages)?

Again, it works fine when called from the shell. It's almost like the shell_exec call isn't waiting for the net/http call to finish.

Any ideas?

Answer 1

I'm not sure on this, but given your explanation, which sounds plausible, have you looked at all at proc_open:

http://us3.php.net/proc_open

Answer 2

Ruby's open-uri requires tempfile , so I'm guessing there's a file ownership conflict between you running your ruby script and the web server running it. Can the web server create a temp file using tempfile ?

Answer 3

Just an FYI, I never really uncovered why this was happening. The best I could deduce was that some type of permission issue was preventing Ruby's open-uri commands from working properly.

I opted for queuing these jobs in a db table and running my ruby script via cron periodically. Everything seems to work fine when the ruby script runs with root/sudo perms.

Answer 4

Run on Linux terminal: sudo -H -u <user> bash -c <your code> where <user> is the Apache's user.

To find Apache's user you can echo("shell_exec(\\"whoami\\")"); inside your code and run it on browser. whoami works on Linux and Windows, but if you're under Windows, the Apache default user is your user. You can test it anyway in case it's different, but I can't tell how to run the code on Windows like if it's Apache running it.

After that you can have a clue of what's happening. In most cases the problem is the Apache's root folder is different from operating system's folder. So when you run a command with absolute path, the OS consider / and Apache consider /var/www/html on Linux, /opt/lampp/htdocs on Xampp(Linux) and C:/xampp/htdocs on Xampp(Windows). You get the idea i think.