Linux Directory Size Issue with C - c

Question

Here is what I need to do:
Write a C program to calculate the total size of the files in a
directory and the sub-directories of the directory. Note that the
total size should include the sizes of sub-directories (directories
are also files) and size of the top-level directory. If a file is a
symbolic link, the symbolic link should not be dereferenced. So the
size of the symbolic link is added to the total size, not the size of
the file pointed by the link. To facilitate testing, your program
should print out ONLY the total size in bytes, i.e., ONE number,
nothing else.
Here is what I have:
#include <sys/stat.h>
#include <sys/types.h>
#include <dirent.h>
#include <string.h>
#include <stdio.h>
int main(int argc, char *argv[]){
char* folder = argv[1];
long length;
DIR* dir_p;
struct dirent* dir_element;
struct stat file_info;
dir_p = opendir(folder);
while(dir_element = readdir(dir_p)){
lstat(dir_element->d_name, &file_info);
length+=file_info.st_size;
printf("%s\n" , dir_element->d_name);
}
return 0;
}
The problem here is that I do not get the right number for some reason. I check the output of my program with du -abc "directory_pathname" call in Ubuntu(Linux).

Answer 1

You never initialize length. Also, you need to actually recurse into directories. Put the while into a function, then call that function for each directory you find (check man stat to figure out how to tell if the file is a directory; I forget the exact test off the top of my head but it's a member of struct stat).