NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON
READDIR(3) Linux Programmer's Manual READDIR(3)
readdir, readdir_r - read a directory
#include <dirent.h>
struct dirent *readdir(DIR *dir);
int readdir_r(DIR *dir, struct dirent *entry, struct dirent **result);
The readdir() function returns a pointer to a dirent structure representing
the next directory entry in the directory stream pointed to by dir. It
returns NULL on reaching the end of the directory stream or if an error
occurred.
On Linux, the dirent structure is defined as follows:
struct dirent {
ino_t d_ino; /* inode number */
off_t d_off; /* offset to the next dirent */
unsigned short d_reclen; /* length of this record */
unsigned char d_type; /* type of file */
char d_name[256]; /* filename */
};
According to POSIX, the dirent structure contains a field char d_name[] of
unspecified size, with at most NAME_MAX characters preceding the terminating
null byte. POSIX.1-2001 also documents the field ino_t d_ino as an XSI
extension. The other fields are unstandardized, and not present on all
systems; see NOTES below for some further details.
The data returned by readdir() may be overwritten by subsequent calls to
readdir() for the same directory stream.
The readdir_r() function is a reentrant version of readdir(). It reads the
next directory entry from the directory stream dir, and returns it in the
caller-allocated buffer pointed to by entry. (See NOTES for information on
allocating this buffer.) A pointer to the returned item is placed in *result;
if the end of the directory stream was encountered, then NULL is instead
returned in *result.
The readdir() function returns a pointer to a dirent structure, or NULL if an
error occurs or end of the directory stream is reached. On error, errno is
set appropriately.
The readdir_r() function returns 0 on success. On error, it returns a
positive error number. If the end of the directory stream is reached,
readdir_r() returns 0, and returns NULL in *result.
EBADF Invalid directory stream descriptor dir.
SVr4, 4.3BSD, POSIX.1-2001.
Only the fields d_name and d_ino are specified in POSIX.1-2001. The remaining
fields are available on many, but not all systems. Under glibc, programs can
check for the availability of the fields not defined in POSIX.1 by testing
whether the macros _DIRENT_HAVE_D_NAMLEN, _DIRENT_HAVE_D_RECLEN,
_DIRENT_HAVE_D_OFF, or _DIRENT_HAVE_D_TYPE are defined.
Other than Linux, the d_type field is available mainly only on BSD systems.
This field makes it possible to avoid the expense of calling stat(2) if
further actions depend on the type of the file. If the _BSD_SOURCE feature
test macro is defined, then glibc defines the following macro constants for
the value returned in d_type:
DT_BLK This is a block device.
DT_CHR This is a character device.
DT_DIR This is a directory.
DT_FIFO This is a named pipe (FIFO).
DT_LNK This is a symbolic link.
DT_REG This is a regular file.
DT_SOCK This is a Unix domain socket.
DT_UNKNOWN The file type is unknown.
If the file type could not be determined, the value DT_UNKNOWN is returned in
d_type.
Since POSIX.1 does not specify the size of the d_name field, and other non-
standard fields may precede that field within the dirent structure, portable
applications that use readdir_r() should allocate the buffer whose address is
passed in entry as follows:
len = offsetof(struct dirent, d_name) +
pathconf(dirpath, _PC_NAME_MAX) + 1
entryp = malloc(len);
(POSIX.1 requires that d_name is the last field in a struct dirent.)
read(2), closedir(3), dirfd(3), ftw(3), offsetof(3), opendir(3), rewinddir(3),
scandir(3), seekdir(3), telldir(3), feature_test_macros(7)
This page is part of release 3.08 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
2008-07-04 READDIR(3)