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OPENDIR(3) Library Functions Manual OPENDIR(3)

opendir, fdopendir, readdir, readdir_r, telldir, seekdir, rewinddir, closedir, dirfd — directory operations

#include <sys/types.h>
#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(const DIR *dirp);

void
seekdir(DIR *dirp, long loc);

void
rewinddir(DIR *dirp);

int
closedir(DIR *dirp);

int
dirfd(DIR *dirp);

The () 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. On failure, NULL is returned and errno is set to indicate the error.

The () function is equivalent to opendir() except that the directory is specified by file descriptor rather than by name. The file offset associated with the file descriptor at the time of the call determines which entries are returned.

Upon successful return from (), 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 directory, other than by means of closedir(), readdir(), readdir_r(), or rewinddir(), the behavior is undefined. Upon calling closedir() the file descriptor shall be closed.

The () 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 () function is a deprecated variant of readdir(). Like readdir(), it 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. readdir_r() returns 0 on success, or an error number if an error occurs; see ERRORS. 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 () function returns the current location associated with the named directory stream dirp. On failure, -1 is returned and errno is set to indicate the error.

The () 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.

The () function resets the position of the named directory stream dirp to the beginning of the directory.

The () 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 () 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)) {
			closedir(dirp);
			return FOUND;
		}
	closedir(dirp);
}
return NOT_FOUND;

The opendir() function will fail if:

[]
The supplied filename is not a directory.

The opendir() function may also fail and set errno for any of the errors specified for the routines fcntl(2), fstat(2), open(2), and malloc(3).

The fdopendir() function will fail if:

[]
The fd argument is not a valid file descriptor open for reading.
[]
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).

close(2), getdents(2), lseek(2), open(2), dir(5)

The opendir(), fdopendir(), readdir(), readdir_r(), telldir(), seekdir(), rewinddir(), closedir(), and dirfd() functions conform to IEEE Std 1003.1-2008 (“POSIX.1”).

The opendir(), readdir(), telldir(), seekdir(), rewinddir(), closedir(), and dirfd() functions appeared in 4.2BSD. The fdopendir() function appeared in OpenBSD 5.0.

The readdir_r() function was intended to provide a thread-safe version of readdir(). However, it was later found to be both unnecessary in the typical usage and unportable due to insufficient buffer sizing guidance. It was therefore officially deprecated in issue 8.

March 23, 2024 OpenBSD-7.6