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Language: Security
Expertise: Beginner

May 31, 1998

Question:
How do you change UNIX file permissions in Java? I've seen it done and I need to replicate it.

Answer:
There is no platform-independent way of changing file permissions in Java. To do so, you either have to write native code, or exec a local program to do the work for you.

The way the programs you've seen have done it is probably using the latter approach. For example:

Runtime runtime = Runtime.getRuntime();
Process chmod;

chmod = runtime.exec("/bin/chmod 755 filename");
chmod.waitFor();

This approach is not recommended for programs that must portable. But it is an acceptable method if your program is only going to run on Unix systems and you just need to get things working.