I was porting a Ruby script to Scala today, and was reintroduced to how shockingly low-level the Java process APIs are.
For example, things you probably take for granted, like:
- Resolving a simple executable name to an absolute path via
PATHvariable - Passing the current process’s environment variables on to the child process
- Managing the stdin, stdout, stderr buffers to ensure they don’t get full (which blocks the child process)
Are not done by Java’s java.lang.Runtime class out-of-the-box. (Which I suppose is understandable, given the APIs must be cross-platform, so cannot make per-platform assumptions.)
This was nonetheless surprising for me, as some of these things I assumed were so basic to process management that it was the OS performing the logic, so they would just magically happen. But no.
So, to the point, Joist has a utility class that is perfect for this: Execute.
I originally wrote it to invoke PgAdmin/MySQL commands to backup/restore the developer’s local database, but since it has come in handy for a number of other things.
The usage is very straight forward:
val result = new Execute("ls")
.arg("-l")
.arg("/some/path")
.toSystemOut()
println(result.exitCode)
So, if you’re doing similar things, you might find it useful. You can check out:
- Execute.java
- ExecuteTest.java
- joist-util in the Joist maven repo
In other news, the ~70 lines of Ruby code I was ported ended up being ~50 lines of Scala code. Nice!
Admittedly, I cheated and put some abstractions that were used by another script into a trait, but that’s even better anyway.