Another Runtime Problem

[Tom Hill]

public static void main(String[] args){
try{
Process a = Runtime.getRuntime().exec("cmd.exe /c dir c:\\software");
BufferedWriter bw= new BufferedWriter(new OutputStreamWriter(a.getOutputStream()));
String[] commands = {"del C:\\file.txt","dir c:\\peanut"};
 
for(int i=0;i<commands.length;i++){
bw.write((commands[i]+"\n"));
}
 
BufferedReader br = new BufferedReader(new InputStreamReader(a.getInputStream()));
StringBuffer sb = new StringBuffer("");
String line;
 
while((line=br.readLine())!=null){
sb.append(line+"\n");
}
System.out.println(sb);
}catch(Exception e){
System.out.println(e);
}
 
}

Am I missing something, the commands in the array dont appear to get processed at all

[JulianInactive KennedyInactive]

This is just a guess at what might be wrong; I haven't tried it. I'm thinking it may be that Windows doesn't like the "\n" on the end of your command string. Newline in Windows is "\r\n".

To fix, either just try that as the rest of your code is tied to Windows anyway or, in the interest of portability , use bw.newLine() or swap your BufferedWriter for a PrintWriter and use println().

Jules

[Tom Hill]

Bizzare - none of those worked Does this happen in Unix too? I've got this working before now and it seems to have magically stopped!!

Tom

[Ernest Friedman-Hill]

Doesn't "cmd /c somecommand" tell cmd.exe to execute "somecommand" and then exit? Maybe you want to save "dir c:\\software" for the "commands" array.

[Tom Hill]

okay it does appear to run a command and the exit, hence why it stops early - but what should be there then?

[Tom Hill]

hmm ive just tried it on a linux machine and im getting the same problems

[William Brogden]

1. If you don't flush the bw stream, the commands may still be in the buffer.
2. You really need to set up a separate Thread to read the output - if the process output doesn't get consumed, it may just sit there.
Bill

[Ernest Friedman-Hill]

Originally posted by Tom Hill:
okay it does appear to run a command and the exit, hence why it stops early - but what should be there then?

Just "cmd.exe".

Regarding doing something similar on Unix -- if you mean running sh -c "some command" and then trying to send more commands: yep, same problem, same reason.

[Tony Morris]

side note: why aren't you using Java to perform what you are attempting?

Your system commands look like a broken approach.

[Tom Hill]

because I wanted to start with easy commnads I know the results of rather than the actuall commands that will be run

[Tom Hill]

Interesting : on windows /k is required to keep the shell open to write commands too. In unix the first command has to be a shell command such a ksh and proceeding commands are written to it and then the new shell dies after leaving.

But:

doing: String[] commands = {"ksh","klog username","password"};
Hangs!
I assumed it might be that a new terminal is created for the password prompt but then: echo password | klog username wouldnt work:
and java doesnt like: commands ={"ksh","echo password | klog user"};
for the same reason - could it be that Java cannot cope with prompts that do not display the shell's input?

[JulianInactive KennedyInactive]

I think it might have something to do with Bill's comment about consuming the process's output streams. See this Javaworld article for more detail.

Jules