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NAME
readdir - read a directory
SYNOPSIS
#include <sys/types.h>
#include <dirent.h>
struct dirent *readdir(DIR *dir);
DESCRIPTION
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-file 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.
RETURN VALUE
The readdir() function returns a pointer to a dirent structure, or NULL
if an error occurs or end-of-file is reached. On error, errno is set
appropriately.
ERRORS
EBADF Invalid directory stream descriptor dir.
CONFORMING TO
SVr4, 4.3BSD, POSIX.1-2001
NOTES
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.
SEE ALSO
read(2), closedir(3), dirfd(3), ftw(3), opendir(3), rewinddir(3),
scandir(3), seekdir(3), telldir(3), feature_test_macros(7)
COLOPHON
This page is part of release 3.01 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/.
2008-06-20 READDIR(3)