fgets에서 segmentation fault가 뜨는데 이유를 모르겠습니다.

#define BUF_SIZE 2500
#define ACTION_ONCE 1001
#define ACTION_WAIT 1002
#define ACTION_RESPAWN 1003
 
 
void check_cmd(char **);
 
int main (int argc, char **argv){
 
  if (argc <= 1)
    {
      fprintf (stderr, "configuration file must specified\n");
      return -1;
    }
 
	char *fileName=argv[1];
	char *str=(char*)malloc(sizeof(char)*BUF_SIZE);
	FILE *fp;
  	if((fp=fopen(fileName,"r"))==NULL){
		fprintf (stderr, "failed to load config file %s \n", fileName);
		return -1;
	}
	while(!feof(fp)){
		fgets(str,BUF_SIZE,fp);//error가 나는 부분
		check_cmd(&str);
 
		printf("%s\n",str);
	}
	free(str);
	fclose(fp);
  return 0;
}
 
void check_cmd(char **str){
	if(*str[0]=='#'){
		*str="# command";
	}
}