Executing (system ...) command requires another 'ENTER' from repl?

[Yasuaki Kudo]

Hi,

I wonder why I need to press ENTER twice in the racket REPL for this command:

racket

Welcome to Racket v7.9 [bc].

> (with-output-to-string (lambda () (system "ls")))

"a.rkt\nfuncs.rkt\nliteral.rkt\nparser.rkt\nparser-test.rkt\nt.rkt\ntuvalu.rkt\n"

>

It executes normally if I run this in a Racket  script as below:

#lang racket

(with-output-to-string (lambda () (system "ls")))

[br...@lojic.com]

The documentation for (system) states:

"The resulting process writes to (current-output-port), reads from (current-input-port), and logs errors to (current-error-port)."

So, I'm guessing that it may be waiting for input. The following does not require an extra enter key:

(parameterize ([current-input-port (open-input-string "")])

  (with-output-to-string (lambda () (system "ls"))))

Also, DrRacket doesn't require an extra enter key, so maybe there is something going on unique to the command line REPL.