linux - Creating named pipes in Java -

i experimenting creating named pipes using java. using linux. however, running problem writing pipe hangs.

    file fifo = fifocreator.createfifopipe("fifo");     string[] command = new string[] {"cat", fifo.getabsolutepath()};     process = runtime.getruntime().exec(command);      filewriter fw = new filewriter(fifo.getabsolutefile());     bufferedwriter bw = new bufferedwriter(fw);     bw.write(boxstring); //hangs here     bw.close();     process.waitfor();     fifocreator.removefifopipe(fifo.tostring()); 

fifocreator:

@override public file createfifopipe(string fifoname) throws ioexception, interruptedexception {     path fifopath = propertiesmanager.gettmpfilepath(fifoname);     process process = null;     string[] command = new string[] {"mkfifo", fifopath.tostring()};     process = runtime.getruntime().exec(command);     process.waitfor();     return new file(fifopath.tostring()); }  @override public file getfifopipe(string fifoname) {     path fifopath = propertiesmanager.gettmpfilepath(fifoname);     return new file(fifopath.tostring()); }  @override public void removefifopipe(string fifoname) throws ioexception {     files.delete(propertiesmanager.gettmpfilepath(fifoname)); } 

i writing string consists of 1000 lines. writing 100 lines work 1000 lines doesn't.

however, if run "cat fifo" on external shell, program proceeds , writes out without hanging. strange how cat subprocess launched program doesn't work.

edit: did ps on subprocess , has status "s".

external processes have input , output need handle. otherwise, may hang, though exact point @ hang varies.

the easiest way solve issue change every occurrence of this:

process = runtime.getruntime().exec(command); 

to this:

process = new processbuilder(command).inheritio().start(); 

runtime.exec obsolete. use processbuilder instead.

update:

inheritio() shorthand redirecting of process's input , output of parent java process. can instead redirect input, , read output yourself:

process = new processbuilder(command).redirectinput(     processbuilder.redirect.inherit).start(); 

then need read process's output process.getinputstream().