DIRECTORY(3)

NAME
opendir, readdir, telldir, seekdir, rewinddir, closedir, dirfd - directory operations

SYNOPSIS
#include <sys/types.h>
#include <dirent.h>
DIR *opendir (const char *filename);
struct dirent *readdir (DIR *dirp);
long telldir (const 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 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 readdir function returns a pointer to the next directory entry. It returns NULL upon reaching the end of the directory or detecting an invalid seekdir operation. The GNO implementation will not return entries for either the current directory (.) or the parent directory (..). Directory entries are defined by the following structure in <sys/dirent.h>:
struct dirent {
	unsigned long	d_fileno;	/* file number of entry */
	unsigned short	d_reclen;	/* length of this record */
	unsigned char	d_type;		/* file type (non-IIgs) */
	unsigned char	d_namlen;	/* length of string in d_name */
	char		d_name[256];	/* name must be no longer than this */
}
The value of d_fileno is, on most architectures, the inode of the current file. Since inodes are not used on any current GS/OS FSTs, this number corresponds to the offset of this file in the current directory. d_reclen is the length of the entire struct dirent. The d_type member is currently set to DT_DIR for directories, DT_REG otherwise. d_namlen is the length of the file name contained in d_name.

Subsequent calls to readdir will overwrite previous results in the struct dirent; if the results must be saved then they should be memcpy'd to a user-defined buffer.

The telldir function returns the current location associated with the named directory stream. The result of a telldir on a stream which has just been opened is undefined.

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. 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.

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).

EXAMPLE
Sample code which searches a directory for entry ``name'' in a case-sensitive manner is:
len = strlen(name);
dirp = opendir(".");
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;

BUGS
The GNO implementation of seekdir and rewinddir rely on the GS/OS call GetDirEntryGS. It is thus possible for these routines to fail. If they do, the error will not be detected until a subsequent readdir is performed.

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

HISTORY
The opendir, readdir, telldir, seekdir, rewinddir, closedir, and dirfd functions appeared in BSD 4.2.