Synopsis

#include <dirent.h>

struct dirent *readdir(DIR *dirp);

int readdir_r(DIR *restrict dirp, struct dirent *restrict entry, struct dirent **restrict result);

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

The type DIR, which is defined in the <dirent.h> header, represents a directory stream, which is an ordered sequence of all the directory entries in a particular directory. Directory entries represent files; files may be removed from a directory or added to a directory asynchronously to the operation of readdir().

The readdir() function shall return a pointer to a structure representing the directory entry at the current position in the directory stream specified by the argument dirp, and position the directory stream at the next entry. It shall return a null pointer upon reaching the end of the directory stream. The structure dirent defined in the <dirent.h> header describes a directory entry. The value of the structure's d_ino member shall be set to the file serial number of the file named by the d_name member. If the d_name member names a symbolic link, the value of the d_ino member shall be set to the file serial number of the symbolic link itself.

The readdir() function shall not return directory entries containing empty names. If entries for dot or dot-dot exist, one entry shall be returned for dot and one entry shall be returned for dot-dot; otherwise, they shall not be returned.

The application shall not modify the structure to which the return value of readdir() points, nor any storage areas pointed to by pointers within the structure. The returned pointer, and pointers within the structure, might be invalidated or the structure or the storage areas might be overwritten by a subsequent call to readdir() on the same directory stream. They shall not be affected by a call to readdir() on a different directory stream. The returned pointer, and pointers within the structure, might also be invalidated if the calling thread is terminated.

If a file is removed from or added to the directory after the most recent call to opendir() or rewinddir(), whether a subsequent call to readdir() returns an entry for that file is unspecified.

The readdir() function may buffer several directory entries per actual read operation; readdir() shall mark for update the last data access timestamp of the directory each time the directory is actually read.

After a call to fork(), either the parent or child (but not both) may continue processing the directory stream using readdir(), rewinddir(),  or seekdir(). If both the parent and child processes use these functions, the result is undefined.

The readdir() function need not be thread-safe.

Applications wishing to check for error situations should set errno to 0 before calling readdir(). If errno is set to non-zero on return, an error occurred.

The readdir_r() function shall initialize the dirent structure referenced by entry to represent the directory entry at the current position in the directory stream referred to by dirp, store a pointer to this structure at the location referenced by result, and position the directory stream at the next entry.

The storage pointed to by entry shall be large enough for a dirent with an array of char d_name members containing at least `NAME_MAX+1` elements.

Upon successful return, the pointer returned at *result shall have the same value as the argument entry. Upon reaching the end of the directory stream, this pointer shall have the value NULL.

The readdir_r() function shall not return directory entries containing empty names.

If a file is removed from or added to the directory after the most recent call to opendir() or rewinddir(), whether a subsequent call to readdir_r() returns an entry for that file is unspecified.

The readdir_r() function may buffer several directory entries per actual read operation; readdir_r() shall mark for update the last data access timestamp of the directory each time the directory is actually read.

Return value

Upon successful completion, readdir() shall return a pointer to an object of type struct dirent. When an error is encountered, a null pointer shall be returned and errno shall be set to indicate the error. When the end of the directory is encountered, a null pointer shall be returned and errno is not changed. If successful, the readdir_r() function shall return zero; otherwise, an error number shall be returned to indicate the error.

Errors

These functions shall fail if:

  • EOVERFLOW - One of the values in the structure to be returned cannot be represented correctly.

These functions may fail if:

  • EBADF - The dirp argument does not refer to an open directory stream.

  • ENOENT - The current position of the directory stream is invalid.

Tests

Untested

Known bugs

None

See Also

  1. Standard library functions
  2. Table of Contents