NAME

opendir, fdopendir, readdir, readdir_r, telldir, seekdir, rewinddir, closedir, fdclosedir, dirfd — directory operations

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <dirent.h>

DIR *
opendir(const char *filename);

DIR *
fdopendir(int fd);

struct dirent *
readdir(DIR *dirp);

int
readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);

long
telldir(DIR *dirp);

void
seekdir(DIR *dirp, long loc);

void
rewinddir(DIR *dirp);

int
closedir(DIR *dirp);

int
fdclosedir(DIR *dirp);

int
dirfd(DIR *dirp);

DESCRIPTION

The opendir() function opens the directory named by filename, associates a directory stream with it and returns a pointer to be used to identify the directory stream in subsequent operations.

The fdopendir() function is equivalent to the opendir() function except that the directory is specified by a file descriptor fd rather than by a name. The file offset associated with the file descriptor at the time of the call determines which entries are returned.

Upon successful return from fdopendir(), the file descriptor is under the control of the system, and if any attempt is made to close the file descriptor, or to modify the state of the associated description other than by means of closedir(), readdir(), readdir_r(), or rewinddir(), the behavior is undefined. Upon calling closedir() the file descriptor is closed. The FD_CLOEXEC flag is set on the file descriptor by a successful call to fdopendir().

The readdir() function returns a pointer to the next directory entry. The directory entry remains valid until the next call to readdir() or closedir() on the same directory stream.

The readdir_r() function provides the same functionality as readdir(), but the caller must provide a directory entry buffer to store the results in. The buffer must be large enough for a struct dirent with a d_name array with {NAME_MAX} + 1 elements. If the read succeeds, result is pointed at the entry; upon reaching the end of the directory result is set to NULL.

The telldir() function returns a token representing the current location associated with the named directory stream. Values returned by telldir() are good only for the lifetime of the directory stream from which they are derived. If the directory is closed and then reopened, prior values returned by telldir() will no longer be valid. Values returned by telldir() are also invalidated by a call to rewinddir().

The seekdir() function sets the position of the next readdir() operation on the directory stream. The new position reverts to the one associated with the directory stream when the telldir() operation was performed.

The rewinddir() function resets the position of the named directory stream to the beginning of the directory.

The closedir() function closes the named directory stream and frees the structure associated with dirp.

The fdclosedir() function is equivalent to the closedir() function except that it returns the file descriptor associated with dirp instead of closing it.

The dirfd() function returns the file descriptor associated with dirp.

EXAMPLES

Sample code which searches a directory for entry ``name'' is:

dirp = opendir(".");
if (dirp == NULL)
	return (ERROR);
len = strlen(name);
while ((dp = readdir(dirp)) != NULL) {
	if (dp->d_namlen == len && strcmp(dp->d_name, name) == 0) {
		(void)closedir(dirp);
		return (FOUND);
	}
}
(void)closedir(dirp);
return (NOT_FOUND);

RETURN VALUES

The opendir() and fdopendir() functions return a pointer to the new directory stream on success and NULL on failure.

The readdir() function returns a pointer to a directory entry on success and NULL on failure. The readdir_r() function returns 0 on success and an error number on failure.

The telldir() function returns a nonnegative value on success and -1 on failure.

The closedir() function returns 0 on success and -1 on failure. The fdclosedir() and dirfd() functions return an open file descriptor on success and -1 on failure.

ERRORS

The opendir() function will fail if:

[EACCES]

Search permission is denied for the component of the path prefix of filename or read permission is denied for filename.

[ELOOP]

A loop exists in symbolic links encountered during resolution of the filename argument.

[ENAMETOOLONG]

The length of the filename argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

[ENOENT]

A component of filename does not name an existing directory or filename is an empty string.

[ENOTDIR]

A component of filename is not a directory.

The fdopendir() function will fail if:

[EBADF]

The fd argument is not a valid file descriptor open for reading.

[ENOTDIR]

The descriptor fd is not associated with a directory.

The readdir() and readdir_r() functions may also fail and set errno for any of the errors specified for the routine getdents(2).

The telldir() function may also fail and set errno for any of the errors specified for the routine realloc(3).

The closedir() function may also fail and set errno for any of the errors specified for the routine close(2).

The dirfd() function will fail if:

[EINVAL]

The dirp argument does not refer to a valid directory stream.

SEE ALSO

close(2), lseek(2), open(2), read(2), dir(5)

STANDARDS

The closedir(), dirfd(), fdopendir(), opendir(), readdir(), readdir_r(), rewinddir(), seekdir() and telldir() functions are expected to conform to IEEE Std 1003.1-2008 (“POSIX.1”). The fdclosedir() function and the d_off, d_reclen and d_type fields of struct dirent are non-standard, and should not be used in portable programs.

HISTORY

The opendir(), readdir(), telldir(), seekdir(), rewinddir(), closedir(), and dirfd() functions appeared in 4.2BSD. The fdopendir() function appeared in FreeBSD 8.0. fdclosedir() function appeared in FreeBSD 10.0.

BUGS

The behaviour of telldir() and seekdir() is likely to be wrong if there are parallel unlinks happening and the directory is larger than one page. There is code to ensure that a seekdir() to the location given by a telldir() immediately before the last readdir() will always set the correct location to return the same value as that last readdir() performed. This is enough for some applications which want to "push back the last entry read", e.g., Samba. Seeks back to any other location, other than the beginning of the directory, may result in unexpected behaviour if deletes are present. It is hoped that this situation will be resolved with changes to getdirentries() and the VFS.