Unable to get output from shell script command in java

Question

I'm running a shell script command in java program using ProcessBuilder, here is my code :

String lastLine = "";

ProcessBuilder processBuilder = new ProcessBuilder("/bin/bash", "-c", "echo $(ps -eo pid,args | grep -v grep | grep -v \"$$"\ | grep feature_service.sh | awk '{print $1}')");

BufferedReader reader =
                    new BufferedReader(new InputStreamReader(process.getInputStream()));

String line;
            while ((line = reader.readLine()) != null) {
                lastLine = line;
            }

Output from this : empty string ("")

But if i run the same command on terminal it is working fine (pid of process).

Please help me.

Does this compile? You've got two unescaped quotes inside a string, in "$$" (instead of \"$$\"). — Klitos Kyriacou
– Klitos Kyriacou, Commented Oct 21, 2016 at 7:07
i'm using this \"$$\" only in my program. thnx i will change here also. — vinni
– vinni, Commented Oct 21, 2016 at 7:16

SubOptimal · Accepted Answer · 2016-10-21 06:57:41Z

1

Following simplified Shell command is working.

ProcessBuilder processBuilder = new ProcessBuilder("/bin/bash", 
    "-c", 
    "ps -eo pid,args|grep [f]eature_service.sh|awk '{print $1}'|tr '\\n' ' '");

ps -eo pid,args - list the process ID and the arguments
grep [f]eature_service.sh - grep for the string feature_service.sh in the arguments, the [f] avoid the multiple usage of grep in the chain
awk '{print $1}' - print the first column of the output, using default whitespace characters as delimiter
tr '\n' ' ' - replace all newline cracaters in the output by a space character

answered Oct 21, 2016 at 6:57

SubOptimal

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3 Comments

vinni Over a year ago

command is working on terminal, but getting null (from bufferedReader) if running through java program.

SubOptimal Over a year ago

@vinni I believe you run it differently. If your run /bin/bash -c echo $(...) in the terminal it returns nothing.

vinni Over a year ago

thnx or help, I'm using pgrep -f feature_service.sh and its working fine.

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