#include <stdio.h>

/* compile with find-no-overflow.c or find-opt.c
 * gcc main.c [find-no-overflow.c | find-opt.c] */

int find(char *pattern, char lineno_flag, char except_flag);

#define ARG_FLAGS X('n', lineno) X('x', except)

/* find pattern given by first arg in lines and print them
 * takes optional flags 
 * -x : print all except matching
 * -n : print line numbers */
int main(int argc, char *argv[])
{
    int i;
    char c;

    /* declare flag variables  */
#define X(c, flag) char flag##_flag = 0;
    ARG_FLAGS
#undef X
    char **parg = argv;
    /* parse flag arguments */
    for (i = 1; *++parg; ) {
        if (**parg != '-' || !(*parg)[1]) {
            argv[i++] = *parg;
            continue;
        }
        while (c = *++parg[0])
            switch (c) {
        #define X(C, flag) case C: flag##_flag = 1; break;
            ARG_FLAGS
        #undef X
            default: 
                printf("error: illegal option -%c\n", c);
                argc = 0;
                break;
            }
        --argc;
    }

    /* illegal arguments */
    if (argc != 2) {
        printf("usage: find ");
    #define X(c, _) printf("[-%c] ", c);
        ARG_FLAGS
    #undef X
        printf("pattern\n");
        return -1;
    }

    char *pattern = argv[1];
    /* verify pattern */
    for (i = 0; (c = pattern[i]) != '\0'; i++)
        if (c == '\n') {
            printf("error: newline in pattern\n");
            return -2;
        }

    int found = find(pattern, lineno_flag, except_flag);
    return found;
}