Question
Last activity: 18 Jul 2017 10:20 EDT
How can I execute a shell script from PRPC?
Hi,
If I have shell script on the filesystem of the machine hosting my JVM, how can I execute it from PRPC? I suspect this will require some java in an activity. Any pointers are appreciated
Thanks.
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Accepted Solution
Updated: 17 Jun 2015 12:54 EDT
Here you go, use the Java ProcessBuilder class to executive OS native scripts, below is an example:
ProcessBuilder pb = new ProcessBuilder("myshellScript.sh", "myArg1", "myArg2");
Map<String, String> env = pb.environment();
env.put("VAR1", "myValue");
env.remove("OTHERVAR");
env.put("VAR2", env.get("VAR1") + "suffix");
pb.directory(new File("myDir"));
Process p = pb.start();
Pegasystems Inc.
GB
Not done this myself - but I would say a Java Step will probably do it : using standard Java APIs - see here: http://stackoverflow.com/questions/525212/how-to-run-unix-shell-script-from-java-code
Alternatively (if you have some control over the shell-script) - you could create a file from PRPC that the Shell Script could poll for.
Pegasystems Inc.
US
I would also consider the business need. Why do you need the shell script? What is the desired functionality? What requires PRPC to be the initiator ?
Accepted Solution
Updated: 17 Jun 2015 12:54 EDT
Here you go, use the Java ProcessBuilder class to executive OS native scripts, below is an example:
ProcessBuilder pb = new ProcessBuilder("myshellScript.sh", "myArg1", "myArg2");
Map<String, String> env = pb.environment();
env.put("VAR1", "myValue");
env.remove("OTHERVAR");
env.put("VAR2", env.get("VAR1") + "suffix");
pb.directory(new File("myDir"));
Process p = pb.start();
MBAFC
CN
Now I have a requirement to run the shell script from the java method in the activity.
I had try as follow but it look's like nothing happend.
=====================================================
try{
//Process pb = new ProcessBuilder("/opt/apl/batch/sample_script.sh").start();
//Process proc = Runtime.getRuntime().exec("/opt/apl/batch/sample_script.sh");
new ProcessBuilder("/opt/apl/batch/sample_script.sh").start();
} catch(java.io.IOException ioEx) {
}
=====================================================
Is there somebody had been successfuly running the unix/linux shell on the prpc.
If you had? could you post your coding?
Pegasystems Inc.
GB
You are swallowing any errors with your empty 'catch' block:
Try re-throwing any exceptions like this:
catch(java.io.IOException ioEx) {
throw new PRRuntimeException(ioEX);
}
And see what error you get.
You may also have fully qualify your Java Class reference:
java.lang.ProcessBuilder
Thanks
John
Updated: 22 Jan 2016 4:41 EST
Pegasystems Inc.
GB
This works on my PRPC719 system running on Linux.
I have a script '/tmp/sample.sh' like this:
#!/bin/sh echo "I was run" >> /tmp/sample.log
I made sure it can run from the Linux command line first:
$ chmod +x /tmp/sample.sh $ /tmp/sample.sh $ tail -f /tmp/sample.log
This shows the script was run:
I was run
I left the 'tail -f' running (to watch for new entries in 'sample.log').
And then created the following Activity,based on your code (I did NOT have to fully qualify the class in this instance - probably because it is in java.lang.*):
Java Code:
This works on my PRPC719 system running on Linux.
I have a script '/tmp/sample.sh' like this:
#!/bin/sh echo "I was run" >> /tmp/sample.log
I made sure it can run from the Linux command line first:
$ chmod +x /tmp/sample.sh $ /tmp/sample.sh $ tail -f /tmp/sample.log
This shows the script was run:
I was run
I left the 'tail -f' running (to watch for new entries in 'sample.log').
And then created the following Activity,based on your code (I did NOT have to fully qualify the class in this instance - probably because it is in java.lang.*):
Java Code:
try{
new ProcessBuilder("/tmp/sample.sh").start();
}
catch(java.io.IOException ioEx) {
throw new PRRuntimeException(ioEx);
}
Saved it, and ran it:
Observed that the 'tail -f' shows the new entry in 'sample.log'
I was run
I was run
So this works: but it is fragile : we aren't capturing any output from the script, or checking the result...which I would recommend you would need to do in any sort of Production environment.
(Consider whether calling a shell script from java is a good solution at all: couldn't you construct an OOTB PRPC Service Rule to output to a queue/file; which a shell script could pick up ? That might be more maintainable in my opinion - and decouples PRPC from having to create and manage lots of workings of the script).
Pegasystems Inc.
GB
It's the user which runs the JVM.
So in my case - my user 'pritj' is running Tomcat:
$ ps -ef|grep java|grep -v grep
pritj 6902 1 6 09:23 ? [...]org.apache.catalina.startup.Bootstrap start
The file my script is writing to is also owned by the same same user:
$ ls -lrt sample.log
-rw-r--r-- 1 pritj pritj 20 2016-01-22 09:36 sample.log
This is another good reason to reconsider whether you really want to make a direct call from Java to create a process: much cleaner to decouple the PRPC Activity from the working of the underlying actual script.
Just have PRPC write a file and have a (quite straightforward) shell script to poll for it maybe ?