real time open(HANDLE,"cmd |");

rouge has asked for the wisdom of the Perl Monks concerning the following question:

Hi ! i'm using open(HANDLE,"cmd |") (with a while(<HANDLE>) {...}) to read and parse what the command "cmd" write to its standard output (simple and logic). My problem is that the commands writes really few datas to STDOUT, and the open (or the pipe ? or the way the "while(<HANDLE>)" is handled by perl ?) is buffered, so i sometimes have to wait about 1 or 2 minutes to have my perl program getting the datas... Is there any simple way to get that stuff being unbuffered (or to flush the buffer, or any other magic thing) ? if there's no easy way, i can still rewrite it "C fashion", with fork and exec, but i'm still not sure if the stdout will be automattically buffered or not... help meeeee !!!

Comment on real time open(HANDLE,"cmd \|");

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Re: real time open(HANDLE,"cmd \|"); by jettero (Monsignor) on Nov 07, 2009 at 16:03 UTC
This is the usual document on the topic: suffering from buffering. -Paul	[reply]
Re: real time open(HANDLE,"cmd \|"); by zwon (Abbot) on Nov 07, 2009 at 16:10 UTC
I think that it's `cmd` buffering its output, so here's not too much you can do in perl. Fix `cmd` to flush it's buffer after every output operation if you can.	[reply] [d/l] [select]
Re^2: real time open(HANDLE,"cmd \|"); by ikegami (Patriarch) on Nov 07, 2009 at 23:21 UTC
About the only thing you can do is fool the program into thinking its connected to a tty rather than a pipe. That will cause most programs to use line buffering. Look into using a pseudo tty. IPC::Run can help there.	[reply]
Re^3: real time open(HANDLE,"cmd \|"); by Anonymous Monk on Dec 28, 2012 at 13:40 UTC
A windows console handle (CONIN$, CONOUT$) is not a pipe handle, it is a character device file handle (TTY handle) to the console input buffer or a console output buffer.	[reply]