Added examples/processes.py by Marcus Cavanaugh

examples/processes.py

+#!/usr/bin/env python
+"""An example on how to communicate with a subprocess.
+
+Written by Marcus Cavanaugh.
+See http://groups.google.com/group/gevent/browse_thread/thread/7fca7230db0509f6
+where it was first posted.
+"""
+
+import gevent
+from gevent import socket
+
+import subprocess
+import errno
+import sys
+import fcntl, os
+
+
+def popen_communicate(args, data='', poll_interval=0.01):
+    """Communicate with the process non-blockingly."""
+    p = subprocess.Popen(args, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+    fcntl.fcntl(p.stdin, fcntl.F_SETFL, os.O_NONBLOCK) # make the file nonblocking
+    fcntl.fcntl(p.stdout, fcntl.F_SETFL, os.O_NONBLOCK) # make the file nonblocking
+
+    bytes_total = len(data)
+    bytes_written = 0
+    while bytes_written < bytes_total:
+        try:
+            # p.stdin.write() doesn't return anything, so use os.write.
+            bytes_written += os.write(p.stdin.fileno(), data[bytes_written:])
+        except IOError, ex:
+            if ex[0] != errno.EAGAIN:
+                raise
+            sys.exc_clear()
+        socket.wait_write(p.stdin.fileno())
+
+    p.stdin.close()
+
+    chunks = []
+
+    while True:
+        try:
+            chunk = p.stdout.read(4096)
+            if not chunk:
+                break
+            chunks.append(chunk)
+        except IOError, ex:
+            if ex[0] != errno.EAGAIN:
+                raise
+            sys.exc_clear()
+        socket.wait_read(p.stdout.fileno())
+
+    p.stdout.close()
+    return ''.join(chunks)
+
+
+if __name__ == '__main__':
+    # run 2 jobs in parallel
+    job1 = gevent.spawn(popen_communicate, 'finger')
+    job2 = gevent.spawn(popen_communicate, 'netstat')
+
+    # wait for them to complete. stop waiting after 2 seconds
+    gevent.joinall([job1, job2], timeout=2)
+
+    # print the results (if available)
+    if job1.ready():
+        print 'finger: %s bytes: %s' % (len(job1.value), repr(job1.value)[:50])
+    else:
+        print 'finger: job is still running'
+    if job2.ready():
+        print 'netstat: %s bytes: %s' % (len(job2.value), repr(job2.value)[:50])
+    else:
+        print 'netstat: job is still running'