Java: Can't execute external exe with arguments

Question

I’m trying to run an external program with arguments. The program can take different types of arguments, for instance avl tip.avl or avl < test.ops<

Answer 1

Thank you both, the below works as expected.

File pipe = new File("test_0.ops");
ProcessBuilder pb = new ProcessBuilder("avl");
pb.redirectInput(pipe);
final Process p = pb.start();

Answer 2

the "<" does not get sent as an argument, but as an input after the program runs

No, that’s not right. It is passed as an argument, just as test_0.avl and test_0.ops are.

[…] the same as just running avl and then typing tip.avl

No, that is never what happens in the shell. The shell will pass tip.avl as the first argument.

That said, it is your shell that special-handles the < sign, as it would special-handle > and |. When you use ProcessBuilder, that special handling will not happen. Your second invocation is equivalent to this in the shell:

avl '<' test_0.ops

This will disable the sepcial meaning of the <. That’s not what you wanted here, of course.

Answer 3

You cannot redirect input like that from Java. Using < is a special shell pipe redirection command.

You will either have to use processBuilder.getOutputStream() to write data to the process, or else you can use redirectInput.