How to execute native shell commands from Java Program

How to execute native shell commands from JAVA

Though it’s not recommended but some time it’s become necessary to execute native operating system or shell command from JAVA, especially if you are doing some kind of reporting or monitoring stuff and required information can easily be found using native command. This is not advised though because then you will lose platform independence which is why we mostly used JAVA.



Anyway if you no choice and you want to execute native commands from JAVA then its good to know that how we can do it, many of you probably know this but for those who don't know and have never done it we will see through an example.





Suppose you want to execute "ls" command in Linux which list down all the files and directory in a folder and you want to do it using JAVA.



In JAVA we have a class called "java.lang.Runtime" which is used to interact with Runtime system has facility to execute any shell command using method exec().



Here is the code sample which can be used to execute any native command from JAVA.



final String cmd = "ls -lrt";



int pid = -1;



try {

    // Run ls command

    Process process = Runtime.getRuntime().exec(cmd);

} catch (Exception e) {

    e.printStackTrace(System.err);

}



This is little nice tip which can be very handy in some specific situation but in by and large its not advised by the very own reason of making JAVA code platform dependence.



as pointed out by Jaroslav sedlacek If not done properly it can easily hang the application. Java and external process communicate through buffers. If buffer fills up, the external process stops and waits until java empties the buffer. Java app has to read both output and error streams of the process to prevent this blocking. There is good util class ProcessBuilder since 1.5 in java or apache commons exec can be used too. 

Source:http://javarevisited.blogspot.com/2011/02/how-to-execute-native-shell-commands.html