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directory.3c (2010 09)

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directory(3C) directory(3C)
NAME
directory: closedir(), opendir(), readdir(), readdir_r(), rewinddir(), seekdir(), telldir() - directory opera-
tions
SYNOPSIS
#include <dirent.h>
DIR *opendir(const char *dirname);
struct dirent *readdir(DIR *dirp);
int readdir_r(DIR *dirp, struct dirent *entry, struct dirent **result);
long int telldir(DIR *dirp);
void seekdir(DIR *dirp, long int loc);
void rewinddir(DIR *dirp);
int closedir(DIR *dirp);
DESCRIPTION
This library package provides functions that allow programs to read directory entries without having to
know the actual directory format associated with the file system. Because these functions allow programs
to be used portably on file systems with different directory formats, this is the recommended way to read
directory entries.
opendir() opens the directory dirname and associates a directory stream with it. opendir()
returns a pointer used to identify the directory stream in subsequent operations.
opendir() uses malloc() to allocate memory.
readdir() returns a pointer to the next directory entry. It returns a NULL pointer upon
reaching the end of the directory or detecting an invalid seekdir() operation.
See dirent (5) for a description of the fields available in a directory entry.
readdir_r() initializes the dirent structure referenced by entry to represent the current
position in the directory stream referenced by dirp, and stores a pointer to this
structure at the location referenced by result.
telldir() returns the current location (encoded) associated with the directory stream to which
dirp refers.
seekdir() sets the position of the next readdir() operation on the directory stream to which
dirp refers. The loc argument is a location within the directory stream obtained
from telldir(). The position of the directory stream is restored to where it was
when telldir() returned that loc value. Values returned by telldir() are
valid only while the DIR pointer from which they are derived remains open. If the
directory stream is closed and then reopened, the telldir() value might be
invalid.
rewinddir() resets the position of the directory stream to which dirp refers 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 have done.
closedir() closes the named directory stream, then frees the structure associated with the DIR
pointer.
APPLICATION USAGE
Users of
readdir_r() should note that readdir_r() now conforms with the POSIX.1c Threads stan-
dard. The old prototype of readdir_r() is supported for compatibility with existing DCE applications
only.
RETURN VALUE
opendir() upon successful completion, returns a pointer to an object of type DIR referring to an
open directory stream. Otherwise, it returns a NULL pointer and sets the global vari-
able errno to indicate the error.
readdir() upon successful completion, returns a pointer to an object of type struct dirent
describing a directory entry. Upon reaching the end of the directory, readdir()
returns a NULL pointer and does not change the value of errno. Otherwise, it
HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

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