Executing CMD Commands via Java

Problem:

Attempting to execute CMD commands through a Java class but facing challenges understanding the code. The user requires guidance on how to execute specific commands, such as changing directories (cd) and running commands within the new directory.

Solution:

One approach to executing processes from alternative directories to the working directory of your Java program is to navigate to the desired directory and execute the process in the same command line. This can be achieved by instructing cmd.exe to run a command line of the form:

cd some_directory && some_program

Code Example:

The following Java code demonstrates changing to a different directory and executing the "dir" command within that directory:

import java.io.*;

public class CmdTest {
    public static void main(String[] args) throws Exception {
        ProcessBuilder builder = new ProcessBuilder(
            "cmd.exe", "/c", "cd \"C:\Program Files\Microsoft SQL Server\" && dir");
        builder.redirectErrorStream(true);
        Process p = builder.start();
        BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
        String line;
        while (true) {
            line = r.readLine();
            if (line == null) {
                break;
            }
            System.out.println(line);
        }
    }
}

Explanation:

• This code employs the ProcessBuilder to execute the command.
• The "redirectErrorStream(true)" call redirects the process's standard error to its standard output, resulting in only one stream to read.

Sample Output:

The provided code produces the following output:

C:\Users\Luke\StackOverflow>java CmdTest
 Volume in drive C is Windows7
 Volume Serial Number is D8F0-C934

 Directory of C:\Program Files\Microsoft SQL Server

29/07/2011  11:03    <dir>          .
29/07/2011  11:03    <dir>          ..
21/01/2011  20:37    <dir>          100
21/01/2011  20:35    <dir>          80
21/01/2011  20:35    <dir>          90
21/01/2011  20:39    <dir>          MSSQL10_50.SQLEXPRESS
               0 File(s)              0 bytes
               6 Dir(s)  209,496,424,448 bytes free</dir>
</dir>
</dir>
</dir>
</dir>
</dir>

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