How to run brew command through java program?

Question

So I just installed the 'brightness' utility package using homebrew (its basically a way to adjust screen brightness through terminal), but I'm having a hard time running this code in java:

    Process p = Runtime.getRuntime().exec("brightness -l");

When I run "brightness -l" through terminal, it gives the current screen brightness level. But when I try the line through java it throws this error:

Exception in thread "main" java.io.IOException: Cannot run program "brew": error=2, No such file or directory

I've tried the following:

    Process p = Runtime.getRuntime().exec("/usr/local/bin/ brightness -l");

but it gives me a permission denied error:

Exception in thread "main" java.io.IOException: Cannot run program "/usr/local/bin/": error=13, Permission denied

So I guess it'll work if I grant permission to regular users to access bin. But thats too risky, is there any other way to do it?

Answer 1

The problem in your method is that you are not running command through bash exclusively. So my Solution would be something like

Runtime.getRuntime().exec("/bin/bash -c brightness -l");

Moreover from it is advisable to use ProcessBuilder instead because usage of Runtime.exec() is now discouraged look the documentation

So my final solution would be :

String[] args = new String[] {"/bin/bash", "-c", "brightness" ,"-l"};
Process proc = new ProcessBuilder(args).start();

for more examples of ProcessBuilder see this topic