dirent.h(7POSIX)

🌸 PROLOG 🌸

Okay bestie, real talk first: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so like, go consult the corresponding Linux manual page for the tea on Linux behavior), or honestly the interface may not even be implemented on Linux at all. 🙈

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✨ NAME ✨

dirent.h — format of directory entries 💅

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🎀 SYNOPSIS 🎀

#include <dirent.h>

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🦋 DESCRIPTION 🦋

So the internal format of directories? Unspecified. Nobody's promising you anything about it, periodt.

The <dirent.h> header shall define the following type:

• DIR — a type representing a directory stream. And heads up, the DIR type may be an incomplete type. (iykyk)

It shall also define the structure dirent, which shall include these members:

ino_t  d_ino       File serial number.
char   d_name[]    Filename string of entry.

The <dirent.h> header shall define the ino_t type as described in <sys/types.h>.

Now, the array d_name is of unspecified size, but it shall contain a filename of at most {NAME_MAX} bytes followed by a terminating null byte. That's the whole vibe.

The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided. 👑

int            alphasort(const struct dirent **, const struct dirent **);
int            closedir(DIR *);
int            dirfd(DIR *);
DIR           *fdopendir(int);
DIR           *opendir(const char *);
struct dirent *readdir(DIR *);
int            readdir_r(DIR *restrict, struct dirent *restrict,
                   struct dirent **restrict);
void           rewinddir(DIR *);
int            scandir(const char *, struct dirent ***,
                   int (*)(const struct dirent *),
                   int (*)(const struct dirent **,
                   const struct dirent **));
void           seekdir(DIR *, long);
long           telldir(DIR *);

The following sections are informative. (Translation: they're the bonus content, not the rules. 🫶)

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💖 APPLICATION USAGE 💖

None.

That's it. That's the section. Nothing. Empty. Iconic of her honestly. 💀

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🌈 RATIONALE 🌈

Information similar to what's in the <dirent.h> header is contained in a file <sys/dir.h> in 4.2 BSD and 4.3 BSD. The equivalent in those implementations of struct dirent from this volume of POSIX.1‐2017 is struct direct. ✨

The filename was changed because the name <sys/dir.h> was also used in earlier implementations to refer to definitions related to the older access method; that produced name conflicts. And the name of the structure was changed because this volume of POSIX.1‐2017 does not completely define what is in the structure, so it could be different on some implementations from struct direct.

Now here's the part where you listen to me, bestie: the name of an array of char of an unspecified size should not be used as an lvalue. So using:

sizeof(d_name)

is incorrect. Use:

strlen(d_name)

instead. 🚨

And like, the array of char d_name is not a fixed size. Implementations may need to declare struct dirent with an array size for d_name of 1, but the actual number of bytes provided matches (or only slightly exceeds) the length of the filename string. Lowkey fascinating, highkey cursed. 😭

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👑 FUTURE DIRECTIONS 👑

None.

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🍓 SEE ALSO 🍓

• <sys_types.h>

The System Interfaces volume of POSIX.1‐2017, alphasort(), closedir(), dirfd(), fdopendir(), readdir(), rewinddir(), seekdir(), telldir()

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💜 COPYRIGHT 💜

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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And that's the whole page, bestie — brought to you by IEEE/The Open Group, dated 2017, filed under dirent.h(7POSIX). Slay, go read a directory. 💅✨🦋