mod_code v.2

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stdbool.h>
#include<errno.h>

extern int errno;

void find_str(const char *str, const char *lookfor)
{
  char *expl = strstr(str, lookfor);

  if(!expl) {
    fprintf(stderr, "Cannot find string");
    exit(1);
  }
}

int main(int argc, char *argv[])
{
  if(argc != 2) {
    fprintf(stderr, "Invalid input\n");
    exit(1);
  }

  FILE* fp;
  char *orig = "func";
  char *new = "printf";
  char *fill = "function";

  int i;

  fp = fopen(argv[1], "r+");
  if(fp = NULL) {
    fprintf(stderr, "Cannot open file\n");
    fclose(fp);
    exit(1);
  }
  else if(errno != 0) {
    fprintf(stderr, "Unexpected error\n");
    fclose(fp);
    exit(1);
  }
  else {
    return 0;
  }

  find_str(fill, "func");

  if(find_str) {
    strcpy(orig, new);
  }
  else {
    fprintf(stderr, "Function failure\n");
    fclose(fp);
    exit(1);
  }

  fclose(fp);

  fp = popen("gcc argv[1] -o compilated", "r");
  if(fp == NULL) {
    fprintf(stderr, "Fuck you bitch!\n");
    pclose(fp);
    return 1;
  }

  pclose(fp);

  return 0;
}