directory: opendir, readdir, readdir64, readdir_r, readdir64_r, telldir, seekdir, rewinddir, closedir -- directory operations


   #include <dirent.h>

DIR *opendir(const char *filename);

struct dirent *readdir(DIR *dirp);

struct dirent64 *readdir64(DIR *dirp);

int readdir_r(DIR *dirp, struct dirent *buf, struct dirent **resp);

int readdir64_r(DIR *dirp, struct dirent64 *buf, struct dirent64 **resp;

long telldir(DIR *dirp);

void seekdir(DIR *dirp, long loc);

void rewinddir(DIR *dirp);

int closedir(DIR *dirp);


opendir opens the directory named by filename and associates a directory stream with it. opendir returns a pointer to be used to identify the directory stream in subsequent operations. The directory stream is positioned at the first entry. A null pointer is returned if filename cannot be accessed or is not a directory, or if it cannot malloc enough memory to hold a DIR structure or a buffer for the directory entries.

readdir and readdir_r return pointers to the next active directory entry and position the directory stream (dirp) at the next entry. Both functions will not return inactive directory entries. NULL is returned upon reaching the end of the directory. resp is a pointer to a pointer to a dirent structure which readdir_r uses to return the directory entry information. If a directory entry is found, resp will be set to point to the structure pointed to by buf. Since the size of the structure may vary depending on the length of d_name, one should provide, through buf, a struct dirent with at least {NAME_MAX} bytes for d_name. On successful completion, readdir_r returns zero. A non-zero return indicates an error and is set to the appropriate errno. readdir and readdir_r typically buffer several directory entries per actual read operation; both functions mark for update the st_atime field of the directory each time the directory is actually read. They return zero with resp set to a null pointer when the end of the directory is reached.

The readdir64 and readdir64_r functions are identical to their counterparts, except that they handle large files.

telldir returns the current location associated with the named directory stream.

seekdir sets the position of the next read operation on the directory stream. The new position reverts to the position associated with the directory stream at the time the telldir operation that provides loc was performed. Values returned by telldir are valid only if the directory has not changed because of compaction or expansion. This situation is not a problem with System V, but it may be a problem with some file system types.

rewinddir resets the position of the named directory stream to the beginning of the directory. It also causes the directory stream to refer to the current state of the corresponding directory, as a call to opendir would.

closedir closes the named directory stream and frees the DIR structure.

Return values

The following errors can occur as a result of these operations.

opendir returns NULL on failure and sets errno to one of the following values:

A component of filename is not a directory.

A component of filename denies search permission.

Read permission is denied on the specified directory.

The maximum number of file descriptors are currently open.

The system file table is full.

filename points outside the allocated address space.

Too many symbolic links were encountered in translating filename.

The length of the filename argument exceeds {PATH_MAX}, or the length of a filename component exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect.

A component of filename does not exist or is a null pathname.

Under the following conditions readdir, readdir64, readdir_r and readdir64_r return one of the following values on failure:

The current file pointer for the directory is not located at a valid entry.

The file descriptor determined by the DIR stream is no longer valid. This result occurs if the DIR stream has been closed.

Under the following condition readdir fails and sets errno to

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

closedir returns -1 on failure and sets errno to the following value:

The file descriptor determined by the DIR stream is no longer valid. This results if the DIR stream has been closed.


dirent(4), getdents(2), intro(2), mkdir(2), rmdir(2)


rewinddir is implemented as a macro, so its function address cannot be taken.

These functions overwrite a buffer per DIR as needed, so applications should copy data or use readdir_r to preserve it.

The older readdir_r interface:

   struct dirent   *readdir_r(DIR *dirp, struct dirent *buf);
is available if _SIMPLE_R is defined.

Considerations for large file support

readdir64 end readdir64_r support large files, but are otherwise identical to readdir and readdir64_r, respectively. For details on programming for large file capable applications, see ``Large File Support'' on intro(2).


Here is a sample program that prints the names of all the files in the current directory:
   #include <stdio.h>
   #include <dirent.h>

main() { DIR *dirp; struct dirent *direntp;

dirp = opendir("."); while ((direntp = readdir(dirp)) != NULL) (void)printf("%s\n", direntp->d_name); closedir(dirp); return (0); }

© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004