Problem Using Java ProcessBuilder to Execute a Piped Command

Question

I'm trying to use Java's ProcessBuilder Class to execute a command that has a pipe in it. For example:

ls -l | grep foo

However, I get an error:

ls: |: no such file or directory

Followed by:

ls: grep: no such file or directory

Even though that command works perfectly from the command line, I can not get ProcessBuilder to execute a command that redirects its output to another. Is there any way to accomplish this?

Answer 1

The simplest way is to invoke the shell with the command line as the parameter. After all, it's the shell which is interpreting "|" to mean "pipe the data between two processes".

Alternatively, you could launch each process separately, and read from the standard output of "ls -l", writing the data to the standard input of "grep" in your example.

Answer 2

This should work:

ProcessBuilder b = new ProcessBuilder("/bin/sh", "-c", "ls -l| grep foo");

To execute a pipeline, you have to invoke a shell, and then run your commands inside that shell.