directory(3C) UNIX System V directory(3C)
NAME
directory: opendir, readdir, telldir, seekdir, rewinddir, closedir -
directory operations
SYNOPSIS
#include <dirent.h>
DIR *opendir (const char *filename);
struct dirent *readdir (DIR *dirp);
long telldir (DIR *dirp);
void seekdir (DIR *dirp, long loc);
void rewinddir (DIR *dirp);
int closedir (DIR *dirp);
DESCRIPTION
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(3C)
enough memory to hold a DIR structure or a buffer for the directory
entries.
readdir returns a pointer to the next active directory entry and
positions the directory stream at the next entry. No inactive entries
are returned. It returns NULL upon reaching the end of the directory or
upon detecting an invalid location in the directory. readdir buffers
several directory entries per actual read operation; readdir marks for
update the statime field of the directory each time the directory is
actually read.
telldir returns the current location associated with the named directory
stream.
seekdir sets the position of the next readdir 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.
10/89 Page 1
directory(3C) UNIX System V directory(3C)
closedir closes the named directory stream and frees the DIR structure.
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:
ENOTDIR A component of filename is not a directory.
EACCES A component of filename denies search permission.
EACCES Read permission is denied on the specified directory.
EMFILE The maximum number of file descriptors are currently
open.
ENFILE The system file table is full.
EFAULT filename points outside the allocated address space.
ELOOP Too many symbolic links were encountered in
translating filename.
ENAMETOOLONG The length of the filename argument exceeds
{PATHMAX}, or the length of a filename component
exceeds {NAMEMAX} while {POSIXNOTRUNC} is in
effect.
ENOENT A component of filename does not exist or is a null
pathname.
readdir returns NULL on failure and sets errno to one of the following
values:
ENOENT The current file pointer for the directory is not
located at a valid entry.
EBADF The file descriptor determined by the DIR stream is
no longer valid. This result occurs if the DIR
stream has been closed.
telldir, seekdir, and closedir return -1 on failure and set errno to the
following value:
EBADF The file descriptor determined by the DIR stream is
no longer valid. This results if the DIR stream has
been closed.
EXAMPLE
Here is a sample program that prints the names of all the files in the
current directory:
Page 2 10/89
directory(3C) UNIX System V directory(3C)
#include <stdio.h>
#include <dirent.h>
main()
{
DIR *dirp;
struct dirent *direntp;
dirp = opendir( "." );
while ( (direntp = readdir( dirp )) != NULL )
(void)printf( "%s\n", direntp->dname );
closedir( dirp );
return (0);
}
10/89 Page 3
directory(3C) UNIX System V directory(3C)
SEE ALSO
getdents(2), dirent(4), mkdir(2), rmdir(2).
NOTES
rewinddir is implemented as a macro, so its function address cannot be
taken.
These functions overwrite the buffer as needed, so applications should
copy data to preserve it.
Page 4 10/89