#include <stdio.h>
#include <string.h>
#include <crypt.h>
#include <unistd.h>
#include <sys/wait.h>

int check (char * pw, char * encrypted)
{
	char * newencrypted = crypt (pw, encrypted);
	if (strcmp (newencrypted, encrypted) == 0)
		return 1;
	return 0;
}

void checkall (char * encrypted)
{
	char pw[10];
	int i;
	printf ("Checking %s\n", encrypted);
	for (i=0; i<10000; ++i) {
		sprintf (pw, "%d", i);
		if (check (pw, encrypted)) {
			printf ("encrypted = %s, real = %s\n", encrypted, pw);
			break;
		}
	}
}

#define MAXPROCS 4

int main (int argc, char ** argv)
{
	int nrprocs = 0;
	int pid;
	FILE * input = stdin;
	char line[100], encrypted[100];
	if (argc > 1)
		input = fopen (argv[1], "r");
	if (!input) {
		perror ("fopen");
		return 1;
	}
	while (1) {
		fgets (line, 100, input);
		sscanf (line, "%s", encrypted);
		if (feof (input))
			break;
		while (nrprocs  >= MAXPROCS) {
			if (wait (NULL) > 0)
				nrprocs --;
		}
		fflush (NULL);
		pid = fork ();
		if (pid < 0) {  /* Error */
			perror ("fork");
			break;
		}
		if (!pid) { /* Child */
			checkall (encrypted);
			return 0;
		}
		/* Parent: Continue with while loop. */
		nrprocs++;
	}
	while (nrprocs)
		if (wait (NULL) > 0)
			nrprocs --;
	return 0;
}