The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group


dirent.h - format of directory entries


#include <dirent.h>


The internal format of directories is unspecified.

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

A type representing a directory stream. The DIR type may be an incomplete type.

It shall also define the structure dirent which shall include the following members:

[XSI][Option Start]
ino_t  d_ino       File serial number. 
[Option End]
char   d_name[]    Filename string of entry. 

[XSI] [Option Start] The <dirent.h> header shall define the ino_t type as described in <sys/types.h>. [Option End]

The array d_name is of unspecified size, but shall contain a filename of at most {NAME_MAX} bytes followed by a terminating null byte.

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 **));
[XSI][Option Start]
void           seekdir(DIR *, long);
long           telldir(DIR *);
[Option End]

The following sections are informative.




Information similar to that in the <dirent.h> header is contained in a file <sys/dir.h> in 4.2 BSD and 4.3 BSD. The equivalent in these implementations of struct dirent from this volume of POSIX.1-2008 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; this produced name conflicts. The name of the structure was changed because this volume of POSIX.1-2008 does not completely define what is in the structure, so it could be different on some implementations from struct direct.

The name of an array of char of an unspecified size should not be used as an lvalue. Use of:


is incorrect; use:



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.





XSH alphasort, closedir, dirfd, fdopendir, readdir, rewinddir, seekdir, telldir


First released in Issue 2.

Issue 5

The DESCRIPTION is updated for alignment with the POSIX Threads Extension.

Issue 6

The Open Group Corrigendum U026/7 is applied, correcting the prototype for readdir_r().

The restrict keyword is added to the prototype for readdir_r().

Issue 7

The alphasort(), dirfd(), and scandir() functions are added from The Open Group Technical Standard, 2006, Extended API Set Part 1.

The fdopendir() function is added from The Open Group Technical Standard, 2006, Extended API Set Part 2.

Austin Group Interpretation 1003.1-2001 #110 is applied, clarifying the definition of the DIR type.

POSIX.1-2008, Technical Corrigendum 1, XBD/TC1-2008/0039 [291], XBD/TC1-2008/0040 [291], XBD/TC1-2008/0041 [291], and XBD/TC1-2008/0042 [206] are applied.

End of informative text.


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