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.Dd January 31, 2026
.Dt DIRECTORY 3
.Os
.Sh NAME
.Nm opendir ,
.Nm fdopendir ,
.Nm readdir ,
.Nm readdir_r ,
.Nm telldir ,
.Nm seekdir ,
.Nm rewinddir ,
.Nm closedir ,
.Nm fdclosedir ,
.Nm dirfd
.Nd directory operations
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In dirent.h
.Ft DIR *
.Fn opendir "const char *filename"
.Ft DIR *
.Fn fdopendir "int fd"
.Ft struct dirent *
.Fn readdir "DIR *dirp"
.Ft int
.Fn readdir_r "DIR *dirp" "struct dirent *entry" "struct dirent **result"
.Ft long
.Fn telldir "DIR *dirp"
.Ft void
.Fn seekdir "DIR *dirp" "long loc"
.Ft void
.Fn rewinddir "DIR *dirp"
.Ft int
.Fn closedir "DIR *dirp"
.Ft int
.Fn fdclosedir "DIR *dirp"
.Ft int
.Fn dirfd "DIR *dirp"
.Sh DESCRIPTION
.Bf -symbolic
The
.Fn readdir_r
interface is deprecated
because it cannot be used correctly unless
.Brq Va NAME_MAX
is a fixed value.
.Ef
.Pp
The
.Fn opendir
function
opens the directory named by
.Fa filename ,
associates a
.Em directory stream
with it
and
returns a pointer to be used to identify the
.Em directory stream
in subsequent operations.
.Pp
The
.Fn fdopendir
function is equivalent to the
.Fn opendir
function except that the directory is specified by a file descriptor
.Fa 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.
.Pp
Upon successful return from
.Fn 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
.Fn closedir ,
.Fn readdir ,
.Fn readdir_r ,
or
.Fn rewinddir ,
the behavior is undefined.
Upon calling
.Fn closedir
the file descriptor is closed.
The
.Dv FD_CLOEXEC
flag is set on the file descriptor by a successful call to
.Fn fdopendir .
.Pp
The
.Fn readdir
function
returns a pointer to the next directory entry.
The directory entry remains valid until the next call to
.Fn readdir
or
.Fn closedir
on the same
.Em directory stream .
.Pp
The
.Fn readdir_r
function
provides the same functionality as
.Fn readdir ,
but the caller must provide a directory
.Fa entry
buffer to store the results in.
The buffer must be large enough for a
.Vt struct dirent
with a
.Va d_name
array with
.Brq Va NAME_MAX
+ 1 elements.
If the read succeeds,
.Fa result
is pointed at the
.Fa entry ;
upon reaching the end of the directory
.Fa result
is set to
.Dv NULL .
.Pp
The
.Fn telldir
function
returns a token representing the current location associated with the named
.Em directory stream .
Values returned by
.Fn telldir
are good only for the lifetime of the
.Em directory stream
from which they are derived.
If the directory is closed and then reopened, prior values returned by
.Fn telldir
will no longer be valid.
Values returned by
.Fn telldir
are also invalidated by a call to
.Fn rewinddir .
.Pp
The
.Fn seekdir
function
sets the position of the next
.Fn readdir
operation on the
.Em directory stream .
The new position reverts to the one associated with the
.Em directory stream
when the
.Fn telldir
operation was performed.
.Pp
The
.Fn rewinddir
function
resets the position of the named
.Em directory stream
to the beginning of the directory.
.Pp
The
.Fn closedir
function
closes the named
.Em directory stream
and frees the structure associated with
.Fa dirp .
.Pp
The
.Fn fdclosedir
function is equivalent to the
.Fn closedir
function except that it returns the file descriptor associated with
.Fa dirp
instead of closing it.
.Pp
The
.Fn dirfd
function
returns the file descriptor associated with
.Fa dirp .
.Sh EXAMPLES
Sample code which searches a directory for entry ``name'' is:
.Bd -literal -offset indent
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);
.Ed
.Sh RETURN VALUES
The
.Fn opendir
and
.Fn fdopendir
functions return a pointer to the new
.Em directory stream
on success and
.Dv NULL
on failure.
.Pp
The
.Fn readdir
function returns a pointer to a directory entry on success and
.Dv NULL
on failure.
The
.Fn readdir_r
function returns 0 on success and an error number on failure.
.Pp
The
.Fn telldir
function returns a nonnegative value on success and -1 on failure.
.Pp
The
.Fn closedir
function returns 0 on success and -1 on failure.
The
.Fn fdclosedir
and
.Fn dirfd
functions return an open file descriptor on success and -1 on failure.
.Sh ERRORS
The
.Fn opendir
function will fail if:
.Bl -tag -width Er
.It Bq Er EACCES
Search permission is denied for the component of the path prefix of
.Fa filename
or read permission is denied for
.Fa filename .
.It Bq Er ELOOP
A loop exists in symbolic links encountered during resolution of the
.Fa filename
argument.
.It Bq Er ENAMETOOLONG
The length of the
.Fa filename
argument exceeds
.Brq Dv PATH_MAX
or
a pathname component is longer than
.Brq Dv NAME_MAX .
.It Bq Er ENOENT
A component of
.Fa filename
does not name an existing directory or
.Fa filename
is an empty string.
.It Bq Er ENOTDIR
A component of
.Fa filename
is not a directory.
.El
.Pp
The
.Fn fdopendir
function will fail if:
.Bl -tag -width Er
.It Bq Er EBADF
The
.Fa fd
argument is not a valid file descriptor open for reading.
.It Bq Er ENOTDIR
The descriptor
.Fa fd
is not associated with a directory.
.El
.Pp
The
.Fn readdir
and
.Fn readdir_r
functions may also fail and set
.Va errno
for any of the errors specified for the routine
.Xr getdents 2 .
.Pp
The
.Fn telldir
function may also fail and set
.Va errno
for any of the errors specified for the routine
.Xr realloc 3 .
.Pp
The
.Fn closedir
function may also fail and set
.Va errno
for any of the errors specified for the routine
.Xr close 2 .
.Pp
The
.Fn dirfd
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa dirp
argument does not refer to a valid directory stream.
.El
.Sh SEE ALSO
.Xr close 2 ,
.Xr lseek 2 ,
.Xr open 2 ,
.Xr read 2 ,
.Xr dir 5
.Sh STANDARDS
The
.Fn closedir ,
.Fn dirfd ,
.Fn fdopendir ,
.Fn opendir ,
.Fn readdir ,
.Fn readdir_r ,
.Fn rewinddir ,
.Fn seekdir
and
.Fn telldir
functions are expected to conform to
.St -p1003.1-2008 .
The
.Fn fdclosedir
function and the
.Fa d_off ,
.Fa d_reclen
and
.Fa d_type
fields of
.Vt struct dirent
are non-standard, and should not be used in portable programs.
.Sh HISTORY
The
.Fn opendir ,
.Fn readdir ,
.Fn telldir ,
.Fn seekdir ,
.Fn rewinddir ,
.Fn closedir ,
and
.Fn dirfd
functions appeared in
.Bx 4.2 .
The
.Fn fdopendir
function appeared in
.Fx 8.0 .
.Fn fdclosedir
function appeared in
.Fx 10.0 .
.Sh BUGS
The behaviour of
.Fn telldir
and
.Fn 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
.Fn seekdir
to the location given by a
.Fn telldir
immediately before the last
.Fn readdir
will always set the correct location to return the same value as that last
.Fn 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
.Fn getdirentries
and the VFS.
