Walking a directory in C

opendir, readdir, closedir: three calls and a loop.

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

int count_entries(const char *path) {
    DIR *dir = opendir(path);
    if (dir == NULL) {
        perror("opendir");
        return -1;
    }

    int count = 0;
    struct dirent *entry;
    while ((entry = readdir(dir)) != NULL) {
        if (strcmp(entry->d_name, ".") == 0 ||
            strcmp(entry->d_name, "..") == 0) {
            continue;
        }
        printf("%s\n", entry->d_name);
        count++;
    }
    closedir(dir);
    return count;
}

How it works

1. readdir returns NULL when the entries run out.
2. The dot and dot-dot entries come back too.
3. The returned struct is reused, so copy what you keep.

Keywords and builtins used here

• DIR
• NULL
• char
• const
• continue
• count_entries
• dirent
• if
• int
• return
• struct
• while

The run, in numbers

Lines

24

Characters to type

413

Tokens

135

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 77 seconds.

Type this snippet

Step 2 of 2 in Files & directories, step 12 of 14 in Systems programming.

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Walking a directory in other languages

• JavaScript