opendir(3)

✨ opendir(3) ✨

okay bestie, pull up a chair, because today we're opening directories 💅 this is a page from the Library Functions Manual and it's giving serious "let me into your filesystem" energy 🎀

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🌸 NAME 🌸

opendir, fdopendir — open a directory

💖 LIBRARY 💖

Standard C library (libc, -lc)

🌈 SYNOPSIS 🌈

#include <sys/types.h>
#include <dirent.h>

DIR *opendir(const char *name);
DIR *fdopendir(int fd);

🦋 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

fdopendir():

Since glibc 2.10:
    _POSIX_C_SOURCE >= 200809L
Before glibc 2.10:
    _GNU_SOURCE

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👑 DESCRIPTION 👑

so opendir() opens a directory stream that corresponds to the directory called name, and it hands you back a pointer to that directory stream. the stream is positioned at the very first entry in the directory. first in line, main character energy, no cutting 💅

fdopendir() is literally opendir()'s sibling, except it returns a directory stream for the directory that the open file descriptor fd is referring to. watch out though bestie 🫶 after a successful call to fdopendir(), fd gets used internally by the implementation, and your application should not be using it for anything else. it's taken. it's booked. it's in a relationship with the library now 😭

🔥 RETURN VALUE 🔥

both opendir() and fdopendir() return a pointer to the directory stream. on error they return NULL, and errno is set to tell you what went wrong. not a slay, but at least it tells you why 💀

💅 ERRORS 💅

• EACCES — permission denied. the door said no 🙈
• EBADF — fd is not a valid file descriptor opened for reading.
• EMFILE — the per-process limit on the number of open file descriptors has been reached. you opened too many doors, bestie 🚪
• ENAMETOOLONG — name was too long.
• ENFILE — the system-wide limit on the total number of open files has been reached.
• ENOENT — directory does not exist, or name is an empty string.
• ENOMEM — insufficient memory to complete the operation.
• ENOTDIR — name is not a directory. it's giving "wrong door" 🥲

⭐ ATTRIBUTES ⭐

for an explanation of the terms used in this section, see attributes(7). (no tables allowed in my group chat era so here it is as a cute lil list ✨)

• Interface: opendir(), fdopendir()
• Attribute: Thread safety
• Value: MT-Safe 🫶

🧚 STANDARDS 🧚

POSIX.1-2008.

🌸 STANDARDS 🌸

(yes bestie there are two STANDARDS sections in this manpage, and I am not skipping a single one — we keep every crumb 🍓)

• opendir() — SVr4, 4.3BSD, POSIX.1-2001.
• fdopendir() — POSIX.1-2008. glibc 2.4.

💜 NOTES 💜

• filename entries can be read from a directory stream using readdir(3).
• the underlying file descriptor of the directory stream can be obtained using dirfd(3).
• opendir() sets the close-on-exec flag for the file descriptor underlying the DIR *. meanwhile fdopendir() leaves the setting of the close-on-exec flag unchanged for the file descriptor, fd. and POSIX.1-200x leaves it unspecified whether a successful call to fdopendir() will set the close-on-exec flag for the file descriptor fd — so like, nobody knows, it's a mystery, it's the vibe 🔮

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🔥 SEE ALSO 🔥

open(2), closedir(3), dirfd(3), readdir(3), rewinddir(3), scandir(3), seekdir(3), telldir(3)

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and that's the whole thing bestie, you ate it all up 👑 this lil page came from Linux man-pages 6.20, dated 2026-02-08 🌈 go forth and open some directories, ily, periodt 💖✨🎀