main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

/*
 * const char* const read only
 * const char* is read/write
 */
int find_str_in_str(const char* const base, const char* const sub)
{
        int base_len = strlen(base);
        int sub_len  = strlen(sub);

        char *tmp_sub = NULL;


        /* allocate enough mem for the max string length */
        if(base_len > sub_len) {
                tmp_sub = malloc(base_len + 1);
        }
        else {
                tmp_sub = malloc(sub_len + 1);
        }


        if(NULL == tmp_sub) {
                fprintf(stderr, "Runtime error (malloc)\n");
                exit(1);
        }

        int i = 0;
        int j = 0;

        for(; i < sub_len; i++) {
                for(; j < base_len; j++) {
                        if(base[j] == sub[i]) {
                                tmp_sub[i] = base[j];
                                /* the first occurance was found */
                                break;
                        }
                }
        }

        tmp_sub[i++] = '\0';

        if(0 == strcmp(sub, tmp_sub)) {
                free(tmp_sub);
                return 1;
        } else {
                free(tmp_sub);
                return 0;
        }
}

int main(int argc, char **argv)
{

        if(argc < 3) {
                fprintf(stderr, "Usage: %s %s %s\n", argv[0], "base", "derived");
                return EXIT_FAILURE;
        }

        fprintf(stdout, "Base :    %s\n", argv[0]);
        fprintf(stdout, "Sub  :    %s\n", argv[1]);

        if(1 == find_str_in_str(argv[1], argv[2])) {
                fprintf(stdout, "Result :    true\n");
        } else {
                fprintf(stdout, "Result :    false\n");
        }

        return EXIT_SUCCESS;
}