NAME
opendir
,
fdopendir
, readdir
,
readdir_r
, telldir
,
seekdir
, rewinddir
,
closedir
, fdclosedir
,
dirfd
—
directory operations
LIBRARY
library “libc”
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
readdir_r
()
interface is deprecated because it cannot be used correctly unless
{NAME_MAX} is a fixed value.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 pointer NULL
is returned
if filename cannot be accessed, or if it cannot
malloc(3) enough memory to hold the whole thing.
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 function returns NULL
upon reaching
the end of the directory or on error. In the event of an error,
errno may be set to any of the values documented for
the
getdirentries(2) system call.
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
readdir_r
() function returns 0 on success or an
error number to indicate failure.
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
DIR
pointer, dirp, 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 the dirp pointer, returning
0 on success. On failure, -1 is returned and the global variable
errno is set to indicate the error.
The
fdclosedir
()
function is equivalent to the closedir
() function
except that this function returns directory file descriptor instead of
closing it.
The
dirfd
()
function returns the integer file descriptor associated with the named
directory stream, see
open(2).
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);
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).
SEE ALSO
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.