lpar · June 17, 2011 20:41 · Jun 17, 2011
diff --git a/timeout.rb b/timeout.rb
@@ -0,0 +1,44 @@
+# Runs a specified shell command in a separate thread.
+# If it exceeds the given timeout in seconds, kills it.
+# Returns any output produced by the command (stdout or stderr) as a String.
+# Uses Kernel.select to wait up to the tick length (in seconds) between 
+# checks on the command's status
+#
+# If you've got a cleaner way of doing this, I'd be interested to see it.
+# If you think you can do it with Ruby's Timeout module, think again.
+def run_with_timeout(command, timeout, tick)
+  output = ''
+  begin
+    # Start task in another thread, which spawns a process
+    stdin, stderrout, thread = Open3.popen2e(command)
+    # Get the pid of the spawned process
+    pid = thread[:pid]
+    start = Time.now
+
+    while (Time.now - start) < timeout and thread.alive?
+      # Wait up to `tick` seconds for output/error data
+      Kernel.select([stderrout], nil, nil, tick)
+      # Try to read the data
+      begin
+        output << stderrout.read_nonblock(BUFFER_SIZE)
+      rescue IO::WaitReadable
+        # A read would block, so loop around for another select
+      rescue EOFError
+        # Command has completed, not really an error...
+        break
+      end
+    end
+    # Give Ruby time to clean up the other thread
+    sleep 1
+
+    if thread.alive?
+      # We need to kill the process, because killing the thread leaves
+      # the process alive but detached, annoyingly enough.
+      Process.kill("TERM", pid)
+    end
+  ensure
+    stdin.close if stdin
+    stderrout.close if stderrout
+  end
+  return output
+end
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