directory.3s

<B>Digital的Unix操作系统VAX 4.2源码</B>

..From teklabs!ogcvax!root  Tue Aug  3 05:14:38 1982
..TH DIRECTORY 3  "OGC Revision  8/02/82"
.TH DIRECTORY 3X 8/1/82
.UC 4.1b Compatability
.SH NAME
opendir, readdir, telldir, seekdir, rewinddir, closedir \- flexible length directory operations
.SH SYNOPSIS
.B #include <dir.h>
.PP
.SM
.B DIR
.B *opendir(filename)
.br
.B char *filename;
.PP
.SM
.B struct direct
.B *readdir(dirp)
.br
.B DIR *dirp;
.PP
.SM
.B long
.B telldir(dirp)
.br
.B DIR *dirp;
.PP
.SM
.B seekdir(dirp, loc)
.br
.B DIR *dirp;
.br
.B long loc;
.PP
.SM
.B rewinddir(dirp)
.br
.B DIR *dirp;
.PP
.SM
.B closedir(dirp)
.br
.B DIR *dirp;
.PP
.SM
.B cc ... -lndir
.SH DESCRIPTION
The purpose of this library is to simulate
the new flexible length directory names of 4.2bsd Unix
on top of the old directory structure of 4.1bsd.
It allows programs to be converted immediately
to the new directory access interface,
so that they need only be relinked
when 4.2bsd becomes available.
.PP
.I opendir
opens the directory named by
.I filename
and associates a
.I directory stream
with it.
.I opendir
returns a pointer to be used to identify the
.I directory stream
in subsequent operations.
The pointer
.SM
.B NULL
is returned if
.I filename
cannot be accessed or is not a directory.
.PP
.I readdir
returns a pointer to the next directory entry.
It returns
.B NULL
upon reaching the end of the directory or detecting
an invalid
.I seekdir
operation.
.PP
.I telldir
returns the current location associated with the named
.I directory stream.
.PP
.I seekdir
sets the position of the next
.I readdir
operation on the
.I directory stream.
The new position reverts to the one associated with the
.I directory stream
when the
.I telldir
operation was performed.
Values returned by
.I telldir
are good only for the lifetime of the DIR pointer from 
which they are derived.
If the directory is closed and then reopened, 
the 
.I telldir
value may be invalidated
due to undetected directory compaction.
It is safe to use a previous
.I telldir
value immediately after a call to
.I opendir
and before any calls to
.I readdir.
.PP
.I rewinddir
resets the position of the named
.I directory stream
to the beginning of the directory.
.PP
.I closedir
causes the named
.I directory stream
to be closed,
and the structure associated with the DIR pointer to be freed.
.PP
See /usr/include/dir.h for a description of the fields available in
a directory entry.
The preferred way to search the current directory for entry "name" is:
.br
.sp
	len = strlen(name);
.br
	dirp = opendir(".");
.br
	for (dp = readdir(dirp); dp != NULL; dp = readdir(dir))
.br
		if (dp->d_namlen == len && !strcmp(dp->d_name, name)) {
.br
			closedir(dirp);
.br
			return FOUND;
.br
		}
.br
	closedir(dirp);
.br
	return NOT_FOUND;
.SH LINKING
This library is accessed by specifying "-lndir" as the
last argument to the compile line, e.g.:
.br
.sp
	cc -o prog prog.c -lndir
.SH "SEE ALSO"
/usr/include/dir.h,
open(2),
close(2),
read(2),
lseek(2)
.SH AUTHOR
Kirk McKusick.
Report problems to mckusick@berkeley or ucbvax!mckusick.