OPENDIR(3) | Library Functions Manual | OPENDIR(3)

# NAME

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

# SYNOPSIS

`#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);

# 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. On failure, `NULL` is returned and errno is set to indicate the error.

The `fdopendir`() 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 `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 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 `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 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 `telldir`() 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 `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.

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)).

# EXAMPLES

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;

# ERRORS

The `opendir`() function will fail if:

[`ENOTDIR`]
  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:

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

# SEE ALSO

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

# STANDARDS

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

# HISTORY

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

# CAVEATS

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 | Debian