Re: creating a block file for file-like object
In message [EMAIL PROTECTED], Iain wrote: Well I did work out *a* solution this way: pipename = os.tmpnam() os.mkfifo(pipename) pid = os.fork() if pid==0: fifoobj = open(pipename,w) fifoobj.write(streamobj.read()) fifoobj.close() os.unlink(pipename) else: TroublesomeFunction(pipename) OK, so TroublesomeFunction is reading from the pipe while the child is writing? Naturally you'd get a block if you tried to do both in the same process. And it doesn't fail very gracefully in that if TroublesomeFunction stops before attempting to open/read the pipe, then the child process stays hung waiting for the other end of the pipe to open. Perhaps the parent should open the pipe for reading, before calling TroublesomeFunction. If the parent then dies, the child will get a broken pipe signal, which by default should kill it. -- http://mail.python.org/mailman/listinfo/python-list
Re: creating a block file for file-like object
Perhaps the parent should open the pipe for reading, before calling TroublesomeFunction. If the parent then dies, the child will get a broken pipe signal, which by default should kill it. Yeah, that seems to work well, I think. Thanks for the help! I also realised the child process was continuing and returning when I didn't really want it to. So for anyone else who stumbles across this, it ended up being pipename = os.tmpnam() os.mkfifo(pipename) pid = os.fork() if pid==0: fifoobj = open(pipename,w) fifoobj.write(streamobj.read()) fifoobj.close() os.unlink(pipename) os._exit(os.EX_OK) else: fifoopen = open(pipename,r) TroublesomeFunction(pipename) -- http://mail.python.org/mailman/listinfo/python-list
Re: creating a block file for file-like object
On Nov 8, 10:00 am, Iain [EMAIL PROTECTED] wrote: On Nov 7, 4:42 pm, Lawrence D'Oliveiro [EMAIL PROTECTED] central.gen.new_zealand wrote: In message [EMAIL PROTECTED], Iain wrote: Can someone give me some pointers as to how I might create some sort of blocking device file or named pipe ... mkfifo /path/to/named/pipe Thanks. I did get that far myself with os.mkfifo - my problem is actually using it. To me it seemed like I wanted to do something like streamobj = urllib.urlopen(http://whereever.com/file;) fifoobj = open(/path/to/named/pipe,w) fifoobj.write(streamobj.read()) TroublesomeFunction(/path/to/named/pipe) But as soon as you get to the second line the code hangs (apparently because of the blocking behaviour of the named pipe). Any pointers here would be much appreciated. Well I did work out *a* solution this way: pipename = os.tmpnam() os.mkfifo(pipename) pid = os.fork() if pid==0: fifoobj = open(pipename,w) fifoobj.write(streamobj.read()) fifoobj.close() os.unlink(pipename) else: TroublesomeFunction(pipename) I'd have to say it doesn't strike me as the BEST solution, but it works. In particular the use of os.tmpnam() gives a warning that its use is a potential security vulnerability, but this is inevitable if taking the named pipe approach (any other suggestions are most welcome, of course). And it doesn't fail very gracefully in that if TroublesomeFunction stops before attempting to open/read the pipe, then the child process stays hung waiting for the other end of the pipe to open. In an interactive python shell you also get some weird behaviour in this situation, but I'm not entirely sure what the exact cause of that is. -- http://mail.python.org/mailman/listinfo/python-list
Re: creating a block file for file-like object
On Nov 7, 4:42 pm, Lawrence D'Oliveiro [EMAIL PROTECTED] central.gen.new_zealand wrote: In message [EMAIL PROTECTED], Iain wrote: Can someone give me some pointers as to how I might create some sort of blocking device file or named pipe ... mkfifo /path/to/named/pipe Thanks. I did get that far myself with os.mkfifo - my problem is actually using it. To me it seemed like I wanted to do something like streamobj = urllib.urlopen(http://whereever.com/file;) fifoobj = open(/path/to/named/pipe,w) fifoobj.write(streamobj.read()) TroublesomeFunction(/path/to/named/pipe) But as soon as you get to the second line the code hangs (apparently because of the blocking behaviour of the named pipe). Any pointers here would be much appreciated. -- http://mail.python.org/mailman/listinfo/python-list
Re: creating a block file for file-like object
In message [EMAIL PROTECTED], Iain wrote: Can someone give me some pointers as to how I might create some sort of blocking device file or named pipe ... mkfifo /path/to/named/pipe -- http://mail.python.org/mailman/listinfo/python-list
