directory(3C) 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. The 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 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.
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directory(3C) 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
{PATH_MAX}, or the length of a filename component
exceeds {NAME_MAX} while (_POSIX_NO_TRUNC) 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.
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directory(3C) directory(3C)
EXAMPLE
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->dname );
closedir( dirp );
return (0);
}
SEE ALSO
getdents(2), dirent(4)
NOTES
rewinddir is implemented as a macro, so its function address cannot
be taken.
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