DIRECTORY(3) BSD Programmer's Manual DIRECTORY(3)
opendir, readdir, readdir_r, telldir, seekdir, rewinddir, closedir, dirfd
- directory operations
#include <sys/types.h>
#include <dirent.h>
DIR *
opendir(const char *filename);
struct dirent *
readdir(DIR *dirp);
int
readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);
long
telldir(const DIR *dirp);
void
seekdir(DIR *dirp, long loc);
void
rewinddir(DIR *dirp);
int
closedir(DIR *dirp);
int
dirfd(DIR *dirp);
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. A null pointer is returned
if filename cannot be accessed, or if malloc(3) cannot allocate enough
memory to hold the entire structure.
The readdir() function returns a pointer to the next directory entry in
the named directory stream dirp. It returns NULL upon reaching the end of
the directory or detecting an invalid seekdir() operation.
The readdir_r() function (much like readdir()) initializes the dirent
structure referenced by entry to represent the next directory entry in
the named directory stream dirp, and stores a pointer to this structure
at the location referenced by result. The storage pointed to by entry
must be large enough for a dirent with a d_name array member containing
at least NAME_MAX plus one elements. On successful return, the pointer
returned at *result will have the same value as the argument entry. Upon
reaching the end of the directory stream, this pointer shall have the
value NULL.
The telldir() function returns the current location associated with the
named directory stream dirp.
The seekdir() function sets the position of the next readdir() operation
on the named directory stream dirp. The new position reverts to the one
associated with the directory stream when the telldir() operation was
performed. 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, the telldir() value may be invalidated due to
undetected directory compaction. It is safe to use a previous telldir()
value immediately after a call to opendir() and before any calls to read-
dir().
The rewinddir() function resets the position of the named directory
stream dirp 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 dirp (see open(2)).
Sample code which searches a directory for entry "name" is:
len = strlen(name);
dirp = opendir(".");
if (dirp) {
while ((dp = readdir(dirp)) != NULL)
if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
(void)closedir(dirp);
return (FOUND);
}
(void)closedir(dirp);
}
return (NOT_FOUND);
close(2), getdirentries(2), lseek(2), open(2), dir(5)
The opendir(), readdir(), telldir(), seekdir(), rewinddir(), closedir(),
and dirfd() functions appeared in 4.2BSD.
MirBSD #10-current June 4, 1993 1