Finally found a wat to set a file nonblocking that works on Irix,

gvanrossum · gvanrossum · commit 0e351f34c516 · 1997-05-12T22:15:52.000Z
Solaris and Linux: use os.O_NONBLOCK.
diff --git a/Lib/test/test_fcntl.py b/Lib/test/test_fcntl.py
@@ -12,9 +12,9 @@
 
 # the example from the library docs
 f = open(filename,'w')
-rv = fcntl.fcntl(f.fileno(), FCNTL.F_SETFL, FCNTL.FNDELAY)
+rv = fcntl.fcntl(f.fileno(), FCNTL.F_SETFL, os.O_NONBLOCK)
 if verbose:
-    print 'Status from fnctl with O_NDELAY: ', rv
+    print 'Status from fnctl with O_NONBLOCK: ', rv
     
 lockdata = struct.pack('hhllhh', FCNTL.F_WRLCK, 0, 0, 0, 0, 0)
 if verbose:
