I decided to give the example as I seem to get this fine as a Java programmer but you still don't seem to be getting what the javadoc is referring to. I wondered whether it was to do with how Java programmers go about naming methods.
I will do two things now, give one very short explanation as to what the method name means as I think this is what is confusing you and then I will copy the long description of the javadoc which perfectly explains it to me. What I would then ask if it still seems inconsistent, point out precisely in that text what is wrong, otherwise there is no more I can do to help you with this but take over the task and complete it.
Treat methods beginning get as getters, they are getting a java object contained in the object the method belongs to. So getInputStream is getting the java object which has data coming into java from the spawned process, this must be of type InputStream. Likewise getOutputStream gets the java object which pipes data out of java to the spawned process, again must be OutputStream.
Now follows is the text from the javadoc, as I said please point out specifically how this is inconsistent in the following text.
getOutputStream public abstract OutputStream getOutputStream()Gets the output stream of the subprocess. Output to the stream is piped into the standard input stream of the
process represented by this Process object.Implementation note: It is a good idea for the output stream to be buffered.
Returns:
the output stream connected to the normal input of the
subprocess.
__________________________________________________________________________________________________________________
getInputStream public abstract InputStream getInputStream()Gets the input stream of the subprocess. The stream obtains data piped from the standard output stream of the
process represented by this Process object.Implementation note: It is a good idea for the input stream to be buffered.
Returns:
the input stream connected to the normal output of the
subprocess.
See Also:
ProcessBuilder.redirectErrorStream()
__________________________________________________________________________________________________________________
getErrorStream public abstract InputStream getErrorStream()Gets the error stream of the subprocess. The stream obtains data piped from the error output stream of the
process represented by this Process object.Implementation note: It is a good idea for the input stream to be buffered.
Returns:
the input stream connected to the error stream of the
subprocess.
See Also:
ProcessBuilder.redirectErrorStream()
On 10/12/10 18:14, qubit wrote:
Mike, no need for the hose example, as I have said I have programmed this in C several times, complete with hooking up pipes. The question was in the java docs, which, as I reread right now, do not imply that getInputStream() connects to the output stream of the child process. It is documented inconsistently as the error stream does connect the stderr to an input stream in the parent. But the input stream appears to have input at both ends of the hose, and the OutputStream appears to have output at both ends of the hose. (like a bad case of the flu -- sorry, couldn't resist...;) Only the error stream appears to be flowing correctly. Perhaps there is a processing step I have missed. Is java's process control based on unix's fork() and exec() model? I see there is a collection of exec methods. However, there is not anything documented in the pages I am looking at that describe how to identify when one is in the child or parent process. Perhaps hooking up pipes is still necessary. This code is going together nicely, but I need to get past this one step. --le ----- Original Message ----- From: "Michael Whapples"<mwhapples@xxxxxxx> To:<brailleblaster@xxxxxxxxxxxxx> Sent: Friday, December 10, 2010 6:01 AM Subject: [brailleblaster] Re: searching java reference I will explain this again, it reads correct to me: InputStream getErrorStream: This is the error output from the process you spawned, it is being read back into your Java code, therefore from the frame of reference of the Java code data is flowing in. InputStream getInputStream: This is standard out of the process, so again the Java code is reading in, data flow is out of the process and into the Java, so InputStream. OutputStream getOutputStream: This is connected to standard in of the process, so Java is sending data out and the process is getting data in. Reading the human generated description of these methods in the javadoc makes it clear to me this is what is going on. I will try and give a different example which may help explain this flow stuff and the direction. If I consider a water tap with a hose pipe (I will refer to as the pipe) which has the other end of the hose pipe in a pool. If you turn on the tap to fill the pool with water you get water flowing along the pipe. Now answer the question is water flowing in or out? Hopefully you will say it depends on what is being referred to, the tap or the pool. Water is flowing out of the tap and into the pool at the same time. So to the tap the pipe is an output and to the pool the same pipe is input. Now let us try and transfer this back to the problem of java.lang.Process. Let us consider the error pipe (as this will not give us any naming problem). Instead of water flowing the pipe we have data, the process is able to be like the tap and output to standard error, our controlling java application is like the pool and is getting input from this pipe. Now if we consider getInputStream, the human part of the javadoc does say this relates to standard output of the spawned process, this makes sense if the method is named for the controlling java code. The spawned process is like the tap in the water example, it outputs to standard output, data flows through the pipe to the java code which reads this data in from the pipe and yes we use InputStreams for that. I hope now you can work out getOutputStream yourself, it doesn't feel worth repeating what I have said. Does the javadoc now make sense to you? Michael Whapples On 09/12/10 23:41, qubit wrote:Sina, the docs say InputStream getErrorStream(); InputStream getInputStream(); OutputStream getOutputStream(); If I'm the parent process and just spawned this process, then the last 2 return types should be switched as I will be writing to input and reading from output. Note that err and out are treated inconsistently. Is this a bug? Do I need to do some obscure pipe operations to get the input and output flowing correctly? Then why was err handled differently from out? You're a java expert, perhaps you can settle this. I am just now getting ready to compile my code, which should tell me if my types are mismatched. I'll be posting to list hopefully soon. TIA --le ----- Original Message ----- From: "Sina Bahram"<sbahram@xxxxxxxxx> To:<brailleblaster@xxxxxxxxxxxxx> Sent: Thursday, December 09, 2010 5:11 PM Subject: [brailleblaster] Re: searching java reference The human part of javadoc can be incorrect, although I find this doubtful. However, the actual return type of the methods, as you've discussed, are not incorrect. They might not meet expectations, but it is automatically generated, so I find it next to impossible for this to be incorrect. Take care, Sina -----Original Message----- From: brailleblaster-bounce@xxxxxxxxxxxxx [mailto:brailleblaster-bounce@xxxxxxxxxxxxx] On Behalf Of qubit Sent: Thursday, December 09, 2010 5:49 PM To: brailleblaster@xxxxxxxxxxxxx Subject: [brailleblaster] searching java reference Is there an easyer way to search the java reference pages by class or by category? I'm having a fun time playing with process and runtime and streams and the like, but some of the docs are indeed incorrect, despite what Mike is saying. I am looking at the link you sent me about the getInputStream() etc methods in class Process. Perhaps I will go look for a download link, but I don't have much space on my hd. I will post what I have so far shortly, but indeed I know the docs are wrong, because they are inconsistent. Compiling will solve the dilemma. --le
