pass.c

#include <unistd.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char **argv) {
	char buf[14];
	char *pass, *salt;
	if(argc < 3) {
		printf("usage: %s password salt\n", argv[0]);
		return 1;
	}
	pass = argv[1];
	salt = argv[2];

	if(strlen(salt) > 8)
		salt[8] = '\0';

	snprintf(buf, 13, "$1$%-6s$", salt);
	printf("%s", crypt(pass, buf));
}