List files in directory and sub directories with size and permission

list_files.c

#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <dirent.h>
#include <string.h>

void list_files();

void main( int argc, char * argv[] ) {
    list_files( argv[1], 0 );
}

void list_files( char *dir, int sub ) {
    DIR *d;
    struct dirent *dir_info;
    struct stat f_stat;
    char *real_path = (char*) malloc( PATH_MAX+1 );
    realpath( dir, real_path );
    strcat( real_path, "/" );

    if( ( d = opendir( dir ) ) == NULL ) {
        perror( "Dir error" );
        exit(1);
    }

    while( ( dir_info = readdir( d ) ) != NULL ) {
        char *file_name = (char*) malloc( PATH_MAX+1 );
        strcpy( file_name, real_path );
        strcat( file_name, dir_info->d_name );
   
        if( stat( file_name, &f_stat ) < 0 ) 
            perror( dir_info->d_name );
        if( S_ISDIR( f_stat.st_mode ) > 0 && strcmp( dir_info->d_name, "." ) != 0 && strcmp( dir_info->d_name, ".." ) != 0 ) {
           list_files( file_name, ( sub + 1 ) );
        } 
        else {
            printf("%s\n", file_name );
            printf( "Size: %d\n", f_stat.st_size );
            printf( "User: %c%c%c\n", 
                f_stat.st_mode & S_IRUSR ? 'R' : '-',
                f_stat.st_mode & S_IWUSR ? 'W' : '-',
                f_stat.st_mode & S_IXUSR ? 'X' : '-'
            );
            printf( "Group: %c%c%c\n", 
                f_stat.st_mode & S_IRGRP ? 'R' : '-',
                f_stat.st_mode & S_IWGRP ? 'W' : '-',
                f_stat.st_mode & S_IXGRP ? 'X' : '-'
            );
            printf( "Others: %c%c%c\n", 
                f_stat.st_mode & S_IROTH ? 'R' : '-',
                f_stat.st_mode & S_IWOTH ? 'W' : '-',
                f_stat.st_mode & S_IXOTH ? 'X' : '-'
            );
            printf( "\n\n" );
        }
        free( file_name );
    }

    free( real_path );
    closedir( d );
}