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readdir

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() 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_UNKNOWN

The file type is unknown.

DT_REG

This is a regular file.

DT_DIR

This is a directory.

DT_FIFO

This is a named pipe, or FIFO.

DT_SOCK

This is a Unix domain socket.

DT_CHR

This is a character device.

DT_BLK

This is a block device.

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)