DIRECTORY(3) BSD Library Functions Manual DIRECTORY(3)
NAME
opendir, fdopendir, readdir, readdir_r, telldir, seekdir, rewinddir, closedir, 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
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 iden-
tify 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, and sets the global variable errno to indicate the error.
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.
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. It 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. Note that the order of the
directory entries vended by readdir() is not specified. Some filesystems may return entries in lexicographic sort order and others may not.
The readdir_r() function provides the same functionality as readdir(), but the caller must provide a directory entry buffer to store the
results in. 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 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.
The seekdir() function sets the position of the next readdir() operation on the directory stream. The new position reverts to the one asso-
ciated 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 dirfd() function returns the integer file descriptor associated with the named directory stream, see open(2). On failure, -1 is returned
and the global variable errno is set to indicate the error.
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);
SEE ALSO
close(2), lseek(2), open(2), read(2), dir(5)
HISTORY
The opendir(), readdir(), telldir(), seekdir(), rewinddir(), closedir(), and dirfd() functions appeared in 4.2BSD. The fdopendir() function
appeared in FreeBSD 8.0.
BSD
April 16, 2008 BSD