C Program to list all files and sub-directories in a directory

In C, we can list all files and sub-directories in a directory using the dirent.h header which provides directory handling functions. This is useful for file system operations and directory traversal programs.

A directory is a container that stores files and other directories in a hierarchical structure. A subdirectory is a directory contained within another directory, creating nested folder structures.

Note: This program requires a POSIX-compliant system (Linux/Unix/macOS). On Windows, you may need to use different headers or compile with specific flags.

Syntax

DIR *opendir(const char *dirname);
struct dirent *readdir(DIR *dirp);
int closedir(DIR *dirp);

Example: List Files in Current Directory

The following program demonstrates how to list all files and subdirectories in the current directory −

#include <stdio.h>
#include <dirent.h>

int main() {
    struct dirent *entry;
    DIR *dir = opendir(".");
    
    if (dir == NULL) {
        printf("Error: Cannot open directory!<br>");
        return 1;
    }
    
    printf("Files and directories in current folder:<br>");
    printf("----------------------------------------<br>");
    
    while ((entry = readdir(dir)) != NULL) {
        printf("%s<br>", entry->d_name);
    }
    
    closedir(dir);
    return 0;
}

How It Works

• opendir(".") opens the current directory ("." represents current directory)
• readdir(dir) reads each entry sequentially and returns a pointer to dirent structure
• entry->d_name contains the name of the file or directory
• closedir(dir) closes the directory stream to free resources

Key Points

• Always check if opendir() returns NULL to handle errors gracefully
• The entries include "." (current directory) and ".." (parent directory)
• Remember to call closedir() to avoid resource leaks
• This function lists both files and subdirectories without distinction

Conclusion

Using dirent.h functions, we can easily traverse directories in C. The opendir(), readdir(), and closedir() functions provide a simple interface for directory listing operations.