c.c

#include<stdio.h>

int main(void) {
	char buf[100];

	scanf("%s", buf);
	printf("%s\n", buf);

	scanf("%s", buf);
	printf("%s\n", buf);

	return 0;
}

master.rkt

#lang racket

(define-values (sp out in err)
  (subprocess #f #f #f
              "/tmp/a.out"
              ))

(displayln "hello" in)
(flush-output in)
(printf "~a" (port->string out))

(displayln "AAAAAAAA" in)
(flush-output in)
(printf "~a" (port->string out))


(close-input-port out)
(close-output-port in)
(close-input-port err)
(subprocess-wait sp)