You can use java.lang.Runtime.exec to run simple code. This gives you back a Process and you can read its standard output directly without having to temporarily store the output on disk.
For example, here's a complete program that will showcase how to do it:
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class testprog {
public static void main(String args[]) {
String s;
Process p;
try {
p = Runtime.getRuntime().exec("ls -aF");
BufferedReader br = new BufferedReader(
new InputStreamReader(p.getInputStream()));
while ((s = br.readLine()) != null)
System.out.println("line: " + s);
p.waitFor();
System.out.println ("exit: " + p.exitValue());
p.destroy();
} catch (Exception e) {}
}
}
When compiled and run, it outputs:
line: ./
line: ../
line: .classpath*
line: .project*
line: bin/
line: src/
exit: 0
as expected.
You can also get the error stream for the process standard error, and output stream for the process standard input, confusingly enough. In this context, the input and output are reversed since it's input from the process to this one (i.e., the standard output of the process).
If you want to merge the process standard output and error from Java (as opposed to using 2>&1 in the actual command), you should look into ProcessBuilder.
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You can use java.lang.Runtime.exec to run simple code. This gives you back a Process and you can read its standard output directly without having to temporarily store the output on disk.
For example, here's a complete program that will showcase how to do it:
import java.io.BufferedReader;
import java.io.InputStreamReader;
public class testprog {
public static void main(String args[]) {
String s;
Process p;
try {
p = Runtime.getRuntime().exec("ls -aF");
BufferedReader br = new BufferedReader(
new InputStreamReader(p.getInputStream()));
while ((s = br.readLine()) != null)
System.out.println("line: " + s);
p.waitFor();
System.out.println ("exit: " + p.exitValue());
p.destroy();
} catch (Exception e) {}
}
}
When compiled and run, it outputs:
line: ./
line: ../
line: .classpath*
line: .project*
line: bin/
line: src/
exit: 0
as expected.
You can also get the error stream for the process standard error, and output stream for the process standard input, confusingly enough. In this context, the input and output are reversed since it's input from the process to this one (i.e., the standard output of the process).
If you want to merge the process standard output and error from Java (as opposed to using 2>&1 in the actual command), you should look into ProcessBuilder.
You can also write a shell script file and invoke that file from the java code. as shown below
{
Process proc = Runtime.getRuntime().exec("./your_script.sh");
proc.waitFor();
}
Write the linux commands in the script file, once the execution is over you can read the diff file in Java.
The advantage with this approach is you can change the commands with out changing java code.
On most Linux distributions you can use update-alternatives like this:
sudo update-alternatives --config java
It will list all packages that provide java command and will let you change it. If you don't want to change it, simply Ctrl-C from it.
There is only one catch - if you installed some java not using official package manager (dpkg/apt-get, rpm/yum), but simply extracted it, update-alternatives will not show it.
You could do:
find / -name java
To find all files. The package manager with your version of Linux should also be able to list them.
If your Main class is in a package called FileManagement, then try:
java -cp . FileManagement.Main
in the parent folder of the FileManagement folder.
If your Main class is not in a package (the default package) then cd to the FileManagement folder and try:
java -cp . Main
More info about the CLASSPATH and how the JRE find classes:
- How Classes are Found
- Setting the class path (Solaris/Linux)
- http://en.wikipedia.org/wiki/Classpath_(Java)
Guys let's understand the syntax of it.
If class file is present in the Current Dir.
java -cp . fileName
If class file is present within the Dir. Go to the Parent Dir and enter below cmd.
java -cp . dir1.dir2.dir3.fileName
If there is a dependency on external jars then,
java -cp .:./jarName1:./jarName2 fileName
Hope this helps.