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Explicitly mention that telldir values are only valid for the lifetime of
the DIR pointer. Pointed out by Klaus Klein.

.\"	$NetBSD: directory.3,v 1.26 2006/05/18 15:30:36 christos Exp $
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.\"     @(#)directory.3	8.1 (Berkeley) 6/4/93
.\"
.Dd May 18, 2006
.Dt DIRECTORY 3
.Os
.Sh NAME
.Nm opendir ,
.Nm readdir ,
.Nm readdir_r ,
.Nm telldir ,
.Nm seekdir ,
.Nm rewinddir ,
.Nm closedir ,
.Nm dirfd
.Nd directory operations
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In dirent.h
.Ft DIR *
.Fn opendir "const char *filename"
.Ft struct dirent *
.Fn readdir "DIR *dirp"
.Ft int
.Fn readdir_r "DIR * restrict dirp" "struct dirent * restrict entry" "struct dirent ** restrict result"
.Ft long
.Fn telldir "DIR *dirp"
.Ft void
.Fn seekdir "DIR *dirp" "long  loc"
.Ft void
.Fn rewinddir "DIR *dirp"
.Ft int
.Fn closedir "DIR *dirp"
.Ft int
.Fn dirfd "DIR *dirp"
.Sh DESCRIPTION
The
.Fn opendir
function
opens the directory named by
.Fa filename ,
associates a
.Em directory stream
with it
and
returns a pointer to be used to identify the
.Em directory stream
in subsequent operations.
The pointer
.Dv NULL
is returned if
.Fa filename
cannot be accessed, or if it cannot
.Xr malloc 3
enough memory to hold the whole thing.
.Pp
The
.Fn readdir
function
returns a pointer to the next directory entry.
It returns
.Dv NULL
upon reaching the end of the directory or detecting an invalid
.Fn seekdir
operation.
.Pp
The
.Fn readdir_r
function
provides the same functionality as
.Fn readdir ,
but the caller must provide a directory
.Fa entry
buffer to store the results in.  If the read succeeds,
.Fa result
is pointed at the
.Fa entry ;
upon reaching the end of the directory
.Fa result
is set to
.Dv NULL .
The
.Fn readdir_r
function
returns 0 on success or an error number to indicate failure.
.Pp
The
.Fn telldir
function
returns the current location associated with the named
.Em directory stream .
.Pp
The
.Fn seekdir
function
sets the position of the next
.Fn readdir
operation on the
.Em directory stream .
The new position reverts to the one associated with the
.Em directory stream
when the
.Fn telldir
operation was performed.
Values returned by
.Fn telldir
are good only for the lifetime of the
.Dv DIR
pointer,
.Fa dirp ,
from which they are derived.
If the directory is closed and then reopened, the
.Fn telldir
value cannot be re-used.
.Pp
The
.Fn rewinddir
function
resets the position of the named
.Em directory stream
to the beginning of the directory.
.Pp
The
.Fn closedir
function
closes the named
.Em directory stream
and frees the structure associated with the
.Fa dirp
pointer,
returning 0 on success.
On failure, \-1 is returned and the global variable
.Va errno
is set to indicate the error.
.Pp
The
.Fn dirfd
function
returns the integer file descriptor associated with the named
.Em directory stream ,
see
.Xr open 2 .
.Sh EXAMPLES
Sample code which searches a directory for entry
.Dq name
is:
.Bd -literal -offset indent
len = strlen(name);
dirp = opendir(".");
if (dirp != NULL) {
	while ((dp = readdir(dirp)) != NULL)
		if (dp-\*[Gt]d_namlen == len \*[Am]\*[Am]
		    !strcmp(dp-\*[Gt]d_name, name)) {
			(void)closedir(dirp);
			return (FOUND);
		}
	(void)closedir(dirp);
}
return (NOT_FOUND);
.Ed
.Sh SEE ALSO
.Xr close 2 ,
.Xr lseek 2 ,
.Xr open 2 ,
.Xr read 2 ,
.Xr dir 5
.Sh STANDARDS
The
.Fn opendir ,
.Fn readdir ,
.Fn rewinddir
and
.Fn closedir
functions conform to
.St -p1003.1-90 .
.Sh HISTORY
The
.Fn opendir ,
.Fn readdir ,
.Fn telldir ,
.Fn seekdir ,
.Fn rewinddir ,
.Fn closedir ,
and
.Fn dirfd
functions appeared in
.Bx 4.2 .