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Ubuntu Java: How to run Linux shell scipt from Java program and fetch back its output

Posted on 2009-07-14
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Last Modified: 2012-05-07
Hi: I am using Java (HTTPUnit) in Linux machine. I am using HTTPUnit multi thread to visit a web application (Hibernate, Spring, tomcat, mysql). Experts in this forum give me the script to see Tomcat JVM memory consumption. Now when I use HTTPUnit to visit a page, then I want to check memory usage by the program themself. And see how much memory consumption it takes. If the memory consumption is bigger, I could write it to some file. My question is from Java program how to run a linux script and how to get output back.

The script is as follows: It could be stored in some executable file called checkTomcatJVM.sh.

ps aux | awk '{print $4"\t"$11}' | sort | uniq -c | awk '{print $2" "$1" "$3}' | grep java
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Question by:JianJunShen
8 Comments
 
LVL 26

Expert Comment

by:ksivananth
ID: 24848897
you can use the Runtime class from java to get the total memory and freememory!

check Runtime.freeMemory()
Runtime.totalMemory
0
 
LVL 6

Expert Comment

by:jwenting
ID: 24848934
Use ProcessBuilder to execute the external process.
Wait for the process to complete, and capture its output stream.
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LVL 14

Expert Comment

by:flob9
ID: 24848936
Runtime.getRuntime().exec(new String[] {"script","param"});
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Author Comment

by:JianJunShen
ID: 24848983
Runtime.getRuntime().exec(new String[] {"script","param"});

This sounds a good solution to run script. But how to fetch output?
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LVL 14

Accepted Solution

by:
flob9 earned 500 total points
ID: 24849040
Something like this :

Process proc = Runtime.getRuntime().exec(new String[] {"script","param"});

byte[] buff = new byte[1024];

InputStream out = proc.getInputStream();
int nb = out.read(buff);


But, as mentionned before, calling external process for this purpose is quite dirty.
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Author Comment

by:JianJunShen
ID: 24849192
Oh; sorry , I push the wrong button. Now the excellent answer would be closed. My mistake.
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Author Closing Comment

by:JianJunShen
ID: 31603225
Excellent answer and very fast.
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LVL 92

Expert Comment

by:objects
ID: 24854763
you need to read in a loop to ensure you get all output written to stdout


http://helpdesk.objects.com.au/java/runtime-exec-locks-up
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