Use getopt

dpu.c

@@ -2,27 +2,38 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <getopt.h>
+
 int main (int argc, char **argv){
 	char name[FILENAME_MAX];
 	FILE *bob,*joe,*moe;
 	int thing, factor, arg;
-	if(argc >= 3){
-		char *end_char;
-		factor = strtol(argv[1], &end_char, 0);
-		if(!*(argv[1]) || *end_char)
-		{
-			fputs("I can haz number?\n", stderr);
+	int modifier;
+	factor=0;
+	while((modifier=getopt(argc,argv,"0123456789"))+1){
+		switch(modifier){
+		case '0': case '1': case '2': case '3': case '4':
+		case '5': case '6': case '7': case '8': case '9':
+			factor=factor*10+modifier-'0';
+			break;
+		default:
+			fputs("You're going to have to be clearer about what you want.\n",stderr);
 			return EXIT_FAILURE;
 		}
-		arg = 2;
-	}else{
-		factor = 9;
-		arg = 1;
 	}
-	if(argc<2){
+	if(factor==0){
+		factor=9;
+	}
+	argc-=optind;
+	argv+=optind;
+	arg=0;
+	if(argc<1){
 		fputs("I pity the fool who don't have an input file!\n",stderr);
 		return EXIT_FAILURE;
 	}
+	if(argc>1){
+		fputs("Be patient, one thing at a time!\n",stderr);
+	}
 	if(strlen(argv[arg]) >= FILENAME_MAX - 4)
 	{
 		fputs("It's a filename, not a novel.\n", stderr);