/* Here's a rough one not relying on any libraries. Example: -wi | -iw //word case insensitive -li | -il //line case insensitive -- file //specify the first filename (you could just get the files as positional arguments in the else statement instead) PS: don't mind the #define's, they're just pasting code :D */ #ifndef OPT_H #define OPT_H //specify option requires argument #define require \ optarg = opt_pointer + 1; \ if (*optarg == '\0') \ { \ if (++optind == argc) \ goto opt_err_arg; \ else \ optarg = argv[optind]; \ } \ opt_pointer = opt_null_terminator; //start processing argv #define opt \ int optind = 1; \ char *opt_pointer = argv[1]; \ char *optarg = NULL; \ char opt_null_terminator[2] = {'\0','\0'}; \ if (0) \ { \ opt_err_arg: \ fprintf(stderr,"option %c requires argument.\n",*opt_pointer); \ return 1; \ opt_err_opt: \ fprintf(stderr,"option %c is invalid.\n",*opt_pointer); \ return 1; \ } \ for (; optind < argc; opt_pointer = argv[++optind]) \ if (*opt_pointer++ == '-') \ { \ for (;;++opt_pointer) \ switch (*opt_pointer) \ { //stop processing argv #define done \ default: \ if (*opt_pointer != '\0') \ goto opt_err_opt; \ else \ goto opt_next; \ break; \ } \ opt_next:; \ } #endif //opt.h #include <stdio.h> #include "opt.h" int main (int argc, char **argv) { #define by_character 0 #define by_word 1 #define by_line 2 int cmp = by_character; int case_insensitive = 0; opt case 'h': puts ("HELP!"); break; case 'v': puts ("fileCMP Version 1.0"); break; case 'i': case_insensitive = 1; break; case 'w': cmp = by_word; case 'l': cmp = by_line; break; case '-':required printf("first filename: %s\n", optarg); break; done else printf ("Positional Argument %s\n", argv[optind]); return 0; } 

 /* Here's a rough one not relying on any libraries. Example: -wi | -iw //word case insensitive -li | -il //line case insensitive -- file //specify the first filename (you could just get the files as positional arguments in the else statement instead) PS: don't mind the #define's, they're just pasting code :D */ #ifndef OPT_H #define OPT_H //specify option requires argument #define require \ optarg = opt_pointer + 1; \ if (*optarg == '\0') \ { \ if (++optind == argc) \ goto opt_err_arg; \ else \ optarg = argv[optind]; \ } \ opt_pointer = opt_null_terminator; //start processing argv #define opt \ int optind = 1; \ char *opt_pointer = argv[1]; \ char *optarg = NULL; \ char opt_null_terminator[2] = {'\0','\0'}; \ if (0) \ { \ opt_err_arg: \ fprintf(stderr,"option %c requires argument.\n",*opt_pointer); \ return 1; \ opt_err_opt: \ fprintf(stderr,"option %c is invalid.\n",*opt_pointer); \ return 1; \ } \ for (; optind < argc; opt_pointer = argv[++optind]) \ if (*opt_pointer++ == '-') \ { \ for (;;++opt_pointer) \ switch (*opt_pointer) \ { //stop processing argv #define done \ default: \ if (*opt_pointer != '\0') \ goto opt_err_opt; \ else \ goto opt_next; \ break; \ } \ opt_next:; \ } #endif //opt.h #include <stdio.h> #include "opt.h" int main (int argc, char **argv) { #define by_character 0 #define by_word 1 #define by_line 2 int cmp = by_character; int case_insensitive = 0; opt case 'h': puts ("HELP!"); break; case 'v': puts ("fileCMP Version 1.0"); break; case 'i': case_insensitive = 1; break; case 'w': cmp = by_word;   break; case 'l': cmp = by_line; break; case '-':required printf("first filename: %s\n", optarg); break; done else printf ("Positional Argument %s\n", argv[optind]); return 0; }