Question

I want to be able to execute an external command from java, eg “ls”, and get the output, both output and error streams, as a string, and in realtime, and in the order they were generated.

So, if the output from the command is something like:

blah     <- to stdout
foo      <- to stderr
bar      <- to stdout

Then, ideally I want the output string, and the realtime output, to look like:

blah
foo
bar

Naive methods produce either:

blah
bar

(ie no stderr output)

or:

blah
bar
foo

(ie the order is rearranged so that the stdout and stderr messages are not interlaced with each other).

Answer 1

Use ProcessBuilder and set redirectErrorStream(true).