223 lines
5.1 KiB
Groff
223 lines
5.1 KiB
Groff
.\" $NetBSD: directory.3,v 1.24 2003/08/07 16:42:47 agc Exp $
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.\"
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.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)directory.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd May 28, 2003
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.Dt DIRECTORY 3
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.Os
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.Sh NAME
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.Nm opendir ,
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.Nm readdir ,
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.Nm readdir_r ,
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.Nm telldir ,
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.Nm seekdir ,
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.Nm rewinddir ,
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.Nm closedir ,
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.Nm dirfd
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.Nd directory operations
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In dirent.h
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.Ft DIR *
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.Fn opendir "const char *filename"
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.Ft struct dirent *
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.Fn readdir "DIR *dirp"
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.Ft int
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.Fn readdir_r "DIR * restrict dirp" "struct dirent * restrict entry" "struct dirent ** restrict result"
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.Ft long
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.Fn telldir "const DIR *dirp"
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.Ft void
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.Fn seekdir "DIR *dirp" "long loc"
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.Ft void
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.Fn rewinddir "DIR *dirp"
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.Ft int
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.Fn closedir "DIR *dirp"
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.Ft int
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.Fn dirfd "DIR *dirp"
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.Sh DESCRIPTION
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The
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.Fn opendir
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function
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opens the directory named by
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.Fa filename ,
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associates a
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.Em directory stream
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with it
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and
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returns a pointer to be used to identify the
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.Em directory stream
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in subsequent operations.
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The pointer
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.Dv NULL
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is returned if
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.Fa filename
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cannot be accessed, or if it cannot
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.Xr malloc 3
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enough memory to hold the whole thing.
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.Pp
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The
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.Fn readdir
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function
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returns a pointer to the next directory entry.
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It returns
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.Dv NULL
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upon reaching the end of the directory or detecting an invalid
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.Fn seekdir
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operation.
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.Pp
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The
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.Fn readdir_r
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function
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provides the same functionality as
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.Fn readdir ,
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but the caller must provide a directory
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.Fa entry
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buffer to store the results in. If the read succeeds,
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.Fa result
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is pointed at the
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.Fa entry ;
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upon reaching the end of the directory
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.Fa result
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is set to
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.Dv NULL .
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The
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.Fn readdir_r
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function
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returns 0 on success or an error number to indicate failure.
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.Pp
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The
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.Fn telldir
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function
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returns the current location associated with the named
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.Em directory stream .
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.Pp
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The
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.Fn seekdir
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function
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sets the position of the next
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.Fn readdir
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operation on the
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.Em directory stream .
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The new position reverts to the one associated with the
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.Em directory stream
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when the
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.Fn telldir
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operation was performed.
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Values returned by
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.Fn telldir
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are good only for the lifetime of the
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.Dv DIR
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pointer,
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.Fa dirp ,
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from which they are derived.
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If the directory is closed and then reopened, the
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.Fn telldir
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value may be invalidated due to undetected directory compaction.
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It is safe to use a previous
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.Fn telldir
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value immediately after a call to
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.Fn opendir
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and before any calls to
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.Fn readdir .
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.Pp
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The
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.Fn rewinddir
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function
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resets the position of the named
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.Em directory stream
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to the beginning of the directory.
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.Pp
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The
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.Fn closedir
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function
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closes the named
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.Em directory stream
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and frees the structure associated with the
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.Fa dirp
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pointer,
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returning 0 on success.
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On failure, \-1 is returned and the global variable
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.Va errno
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is set to indicate the error.
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.Pp
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The
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.Fn dirfd
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function
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returns the integer file descriptor associated with the named
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.Em directory stream ,
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see
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.Xr open 2 .
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.Sh EXAMPLES
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Sample code which searches a directory for entry
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.Dq name
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is:
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.Bd -literal -offset indent
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len = strlen(name);
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dirp = opendir(".");
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if (dirp != NULL) {
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while ((dp = readdir(dirp)) != NULL)
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if (dp-\*[Gt]d_namlen == len \*[Am]\*[Am]
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!strcmp(dp-\*[Gt]d_name, name)) {
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(void)closedir(dirp);
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return (FOUND);
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}
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(void)closedir(dirp);
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}
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return (NOT_FOUND);
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.Ed
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.Sh SEE ALSO
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.Xr close 2 ,
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.Xr lseek 2 ,
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.Xr open 2 ,
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.Xr read 2 ,
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.Xr dir 5
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.Sh STANDARDS
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The
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.Fn opendir ,
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.Fn readdir ,
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.Fn rewinddir
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and
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.Fn closedir
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functions conform to
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.St -p1003.1-90 .
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.Sh HISTORY
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The
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.Fn opendir ,
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.Fn readdir ,
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.Fn telldir ,
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.Fn seekdir ,
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.Fn rewinddir ,
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.Fn closedir ,
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and
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.Fn dirfd
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functions appeared in
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.Bx 4.2 .
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