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Java RunTime exec method's Usage

Posted on 2009-07-14
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Last Modified: 2012-05-07
Hi; I try to use run following script by Runtime.getRuntime.exec. But I do not know how to write arguments.

String[] cmdArray = new String[]{"ps","awk","sort","uniq","awk","grep"};
String[] parameters = new String[]{"aux", "'{print $4 \"\\t\"$11}'"....",null,"-c","'{print $2\" \"$1\" \"$3}'","java"};
       
Process proc = Runtime.getRuntime.exect(cmdArray,parameters);

Am I right?

ps aux | awk '{print $4"\t"$11}' | sort | uniq -c | awk '{print $2" "$1" "$3}' | grep java
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Question by:JianJunShen
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15 Comments
 
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Expert Comment

by:a_b
ID: 24850670
What is the error/issue that occurs when you run this? looks okay to me.
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Assisted Solution

by:CEHJ
CEHJ earned 150 total points
ID: 24850675
With a command as complex as that, you would be much better advised to put it in a shell script and Runtime.exec that

But see

http://www.javaworld.com/javaworld/jw-12-2000/jw-1229-traps.html
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Assisted Solution

by:CEHJ
CEHJ earned 150 total points
ID: 24850700
That would be


String[] args = { "/bin/bash", "x.sh" };

Process p = Runtime.getRuntime().exec(args);

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Author Comment

by:JianJunShen
ID: 24851464
where shall I put script file(x.sh)?

String[] args = { "/bin/bash", "x.sh" };
Process p = Runtime.getRuntime().exec(args);
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Expert Comment

by:CEHJ
ID: 24851509
Well a safe place would be in your home directory
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Author Comment

by:JianJunShen
ID: 24857276
well, if one use eclipse, it is better to put in project root directory. Pararel to src folder.
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Expert Comment

by:CEHJ
ID: 24857313
:-)

btw, my comment at http:#24850675 is devoted to getting output
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Accepted Solution

by:
nkiggs earned 350 total points
ID: 24867139
Hi,

To run complex commands you can simulate your multiple command line arguments with a bufferedwriter writing to the shell you create. So you will have all the commands like:

/bin/sh
cd ..
pwd
exit

to create a shell(or you can use /bin/csh) go one directory backwards(cd ..) and then finally print the working directory (pwd) and finally exit (exit) after reading with the bufferedreader output from pwd command. Code example below to do this. Alter to suite the order you would type your commands in your shell script.
  	public int runProcess(){

      	// code to commence processing		

		String line;

		File wd = new File("/bin");	//location of sh executable 

		Process proc = null; 

		

		try { 

			proc = Runtime.getRuntime().exec("/bin/sh", null, wd); 

		} 

		catch (IOException e) { 

			e.printStackTrace(); 

		} 

		

		if (proc != null) { 

			BufferedReader in = new BufferedReader(new InputStreamReader(proc.getInputStream())); 

			PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(proc.getOutputStream())), true); 

			out.println("cd ..");	

			out.println("pwd");				

			out.println("exit"); 

			try { 	

				int x = 0;

				while ((line = in.readLine()) != null) { 

					if (x > -1){

						System.out.println(line + "\n");

					}

					x++;				

				} 

				proc.waitFor(); 

				in.close(); 

				out.close(); 

				proc.destroy(); 

			} 

			catch (Exception e) { 

				e.printStackTrace(); 

			} 

		}      		

   	}

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Expert Comment

by:nkiggs
ID: 24867188
Hi,

You can simulate all the commands you will normally enter into your shell script window by using both BufferedReader and BufferedWriter simultaneously. Therefore, your application would operate as if you are entering commands manually (BufferedWriter) and get all the output as you enter commands (BufferedReader).

This output can be manipulated with a variable x that tracks the number of lines outputed and you can use this output by manipulating the string "line".

See my comment on the question.

Regards,

nkiggs
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Expert Comment

by:CEHJ
ID: 24874504
nkiggs probably didn't intend to object i'd guess
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Author Comment

by:JianJunShen
ID: 24874618
I think ID:24867139 is the best solution.       ID:24850700 is assistant answer. It is also a good one.
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Author Closing Comment

by:JianJunShen
ID: 31603292
Experts answer are excellent.
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LVL 86

Expert Comment

by:CEHJ
ID: 24874652
The late addition is only appropriate when you for some reason want to run an interactive shell from within Java, which was certainly not mentioned as a requirement...
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Expert Comment

by:CEHJ
ID: 24874657
*Is* it a requirement JianJunShen?
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