// edtest.cpp
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <wait.h>
int main(int argc, char** argv) {
	int p[2];
	//printf("[0] making a pipe\n");
	pipe(p);
	char* filename = argv[1];
	//printf("[0] forking\n");
	pid_t cpid = fork();
	if(cpid == -1) {
		fprintf(stderr,"fork failed\n");
		exit(2);
	}
	if(cpid == 0) {
		//printf("[1] closing fds\n");
		close(0);
		close(1);
#ifndef WORKING
		close(2); // if you comment out this line, the program works fine
#endif
		dup2(p[0], 0);

		//printf("[1] execlp \n");
		execlp("ed", "ed", filename, 0);
		exit(1); // we only reach here in case of an error!
	}
	//printf("[0] opening pipe\n");
	FILE *cmd = fdopen(p[1], "w");
	//printf("[0] sending commands\n");
	fprintf(cmd, ",s/hello/goodbye/g\n");
	fprintf(cmd, "w\n");
	fprintf(cmd, "Q\n");
	//printf("[0] flushing commands\n");
	fflush(cmd);
	int status;
	//printf("[0] checking status \n");
	waitpid(0, &status, 0);
	if(WIFEXITED(status)) {
		fprintf(stderr, "ed retval=%d\n",WEXITSTATUS(status));
	} else {
		fprintf(stderr, "ed terminated abnormally\n");
	}
	return 0;
}