NAME

directory: opendir, readdir, telldir, seekdir, rewinddir, closedir − directory operations

SYNOPSIS

#include <sys/types.h>
#include <dirent.h>

DIR ∗opendir (filename)
char ∗filename;

struct dirent ∗readdir (dirp)
DIR ∗dirp;

long telldir (dirp)
DIR ∗dirp;

void seekdir (dirp, loc)
DIR ∗dirp;
long loc;

void rewinddir (dirp)
DIR ∗dirp;

void closedir(dirp)
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 pointer NULL is returned if filename cannot be accessed or is not a directory, or if it cannot malloc(3X) enough memory to hold a DIR structure or a buffer for the directory entries. 

readdir returns a pointer to the next active directory 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. 

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 one associated with the directory stream when the telldir operation was performed from which loc was obtained.  Values returned by telldir are good only if the directory has not changed due to compaction or expansion.  This is not a problem with System V, but it may be with some file system types. 

rewinddir resets the position of the named directory stream to the beginning of the directory. 

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

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

opendir:

[ENOTDIR] A component of filename is not a directory. 

[EACCES] A component of filename denies search permission. 

[EMFILE] The maximum number of file descriptors are currently open. 

[EFAULT] filename points outside the allocated address space. 

readdir:

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[EBADF] The file descriptor determined by the DIR stream is no longer valid.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

telldir, seekdir, and closedir:

[EBADF] The file descriptor determined by the DIR stream is no longer valid.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

EXAMPLE

Sample code which searches a directory for entry name:

dirp = opendir( "." );
while ( (dp = readdir( dirp )) != NULL )
if ( strcmp( dp->d_name, name ) == 0 )
{
closedir( dirp );
return FOUND;
}
closedir( dirp );
return NOT_FOUND;

SEE ALSO

getdents(2), dirent(4)

WARNINGS

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

September 02, 1992