CODEWITHSUNDEEP
bashtailcat
princess of persia
princess of persia

Reputation: 2232

Unix cat and tail for output of java program

I have a java program that takes time to execute and I have to make 10 runs of it and I am interested in only last 5 lines of the output, the actual output runs in hundreds of lines. Since I want to average the output I want tail -5 for run into a file. Also one of the parameters (--random) in my arguments keep changing in each run.

I am doing the following:

for i in {1..10} ; do cat output| tail -5 | java -cp src.Tagger.java --random $1; done

Sorry I am really bad at bash.

Upvotes: 1

Views: 1486

Answers (2)

Stephen Ostermiller
Stephen Ostermiller

Reputation: 25524

You want the output of your java program to go to output first, then you need to tail the file. It looks like you are currently feeding output into your java program as input. I don't think that is what you want. Try this instead:

for i in {1..10}
do 
    java -cp src.Tagger.java --random $1 > output;
    tail -5 output;
done

I also have my doubts that you have the java command correct. You shouldn't specify .java for the file name when running the java file. It needs to run from the compiled .class file and the java command assumes .class, so it isn't needed on the command line. You also are using -cp (classpath) but don't appear to be giving it an argument. I'd expect the java command to be more like:

java -cp classesdir com.mydomain.myapp.Tagger

Upvotes: 1

that other guy
that other guy

Reputation: 123490

You should make sure you can execute your java program at all first. You can't execute a .java file directly, it has to be compiled.

If you have the file src/Tagger.java, you can try to compile it with 

javac -cp src src/Tagger.java

but if it requires other libraries or build systems, it might be completely different. If you downloaded this app, see the project documentation.

This should silently produce a src/Tagger.class. Once you have this, you can try to run it with

java -cp src Tagger --random 1234

though again, if it has dependencies on libraries, it'll be different.

If that works, you can finally start trying to run it in a loop:

for i in {1..10}
do 
    cat output| tail -5 | java -cp src Tagger --random 1234
done

Upvotes: 1

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