1 files changed, 13 insertions, 7 deletions
diff --git a/count_nucleobases.c b/count_nucleobases.c
index 6edf5e8..d21a2d2 100755
--- a/count_nucleobases.c
+++ b/count_nucleobases.c
@@ -2,14 +2,18 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdint.h>
-main() {
+int main(int argc, char **argv) {
 
-long unsigned long a = 0;
-long unsigned long c = 0;
-long unsigned long g = 0;
-long unsigned long t = 0;
+  long unsigned long a = 0;
+  long unsigned long c = 0;
+  long unsigned long g = 0;
+  long unsigned long t = 0;
 
-FILE *fh = fopen("dna.txt", "r" );
+  if(argc != 2) {
+    printf("Please supply a filename, and only a filename\n");
+    exit(EXIT_FAILURE);
+  }
+  FILE *fh = fopen(argv[1], "r" );
   if(fh == NULL) {
     fprintf(stderr, "could not open dna.txt\n");
     exit(EXIT_FAILURE);
@@ -37,5 +41,7 @@ FILE *fh = fopen("dna.txt", "r" );
     }
   }
 
-  printf("A:%lu\nC:%lu\nG:%lu\nT:%lu\n", a, c, g, t);
+  printf("A:%llu\nC:%llu\nG:%llu\nT:%llu\n", a, c, g, t);
+
+  return EXIT_SUCCESS;
 }