ftw.3

wu-ftpd类unix下的ftp服务器,可用于嵌入式系统

.\"
.\" Copyright (c) 1999,2000 WU-FTPD Development Group. 
.\" All rights reserved.
.\" 
.\" Portions Copyright (c) 1980, 1985, 1988, 1989, 1990, 1991, 1993, 1994 
.\" The Regents of the University of California.  Portions Copyright (c) 
.\" 1993, 1994 Washington University in Saint Louis.  Portions Copyright 
.\" (c) 1996, 1998 Berkeley Software Design, Inc.  Portions Copyright (c) 
.\" 1998 Sendmail, Inc.  Portions Copyright (c) 1983, 1995, 1996, 1997 Eric 
.\" P. Allman.  Portions Copyright (c) 1989 Massachusetts Institute of 
.\" Technology.  Portions Copyright (c) 1997 Stan Barber.  Portions 
.\" Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997 Free Software 
.\" Foundation, Inc.  Portions Copyright (c) 1997 Kent Landfield. 
.\"
.\" Use and distribution of this software and its source code are governed 
.\" by the terms and conditions of the WU-FTPD Software License ("LICENSE"). 
.\"
.\"     $Id: ftw.3,v 1.4 2000/07/01 18:40:49 wuftpd Exp $
.\"
.TH TREEWALK 3 August 4, 1988
.UC 4
.SH NAME
ftw, treewalk \- tree walk
.SH SYNOPSIS
.nf
.B #include <ftw.h>
.PP
.B ftw(path, function, maxfds)
.B char *path;
.B int (*function)(), maxfds;

.B treewalk(path, function, maxfds, options)
.B char *path;
.B int (*function)(), maxfds, options;
.fi
.SH DESCRIPTION
.PP
The \fItreewalk\fP call descends the directory hierarchy rooted in
\fIpath\fP, visiting each node in turn.  Visiting a node consists of
calling the routine \fIfunction\fP with three arguments.  The first
is the current path name, the second a pointer to a stat structure
containing information about the path name, and the third a flag
value.  The declaration of the function may be as follows:
.nf

	#include <sys/stat.h>

	function(path, st, flag)
	char *path;
	struct stat *st;
	int flag;
.fi
.PP
The \fIflag\fP value will be one the following values, as specified in
<\fIftw.h\fP>.
.PP
.RS
 FTW_F		a regular file
 FTW_D		a directory
 FTW_D2	second visit to a directory
 FTW_DNR	an unreadable directory
 FTW_NS	an unknown type, the stat failed
.RE
.PP
If the flag value is \fIFTW_NS\fP, the contents of the stat buffer are
undefined.
.PP
\fIMaxfds\fP governs the number of file descriptors that \fItreewalk\fP may
use.  If passed as -1, no limit is set.  Unless \fIfunction\fP needs
to open files, -1 is the suggested behavior.
.PP
\fIOptions\fP is a bit mask which changes the behavior of \fItreewalk\fP.
Its value is set by or'ing together any of the following values specified
in <\fIftw.h\fP>.
.PP
.RS
 FTW_CHDIR		\fItreewalk\fP may change directories
 FTW_DIRLAST		visit the node after its descendents
 FTW_SYMLINK	follow symbolic links
.RE
.PP
\fIFTW_CHDIR\fP allows \fItreewalk\fP to descend the tree using the
\fIchdir\fP(2) system call.  This makes \fItreewalk\fP run much faster.
A side effect of this flag is that all path names passed to \fIfunction\fP
are relative, not absolute.
.PP
By default, \fItreewalk\fP does a depth-first search, visiting each node
before any of its descendents.  If \fIfunction\fP returns any other value
than 0 or -1, \fItreewalk\fP will not continue, but will return this value
to its caller.  If the returned value is -1, \fItreewalk\fP will continue,
but no descendents of the current node will be visited.  The
\fIFTW_DIRLAST\fP flag causes \fItreewalk\fP to visit the node again after
all of its descendents have been visited.  The second visit to the directory
will call \fIfunction\fP with the \fIFTW_D2\fP flag instead of \fIFTW_D\fP.
.PP
If \fIFTW_SYMLINK\fP is set, \fItreewalk\fP will pass the result of a
\fIstat\fP(2) call to \fIfunction\fP, rather than an \fIlstat\fP(2) call.
In the case of symbolic links pointing to directories, \fItreewalk\fP
will continue down the directory tree pointed to by the link.  If
\fItreewalk\fP is unable to indirect through the link, the node will
be ignored and \fIfunction\fP will not be called.  It should also be
noted that if the symbolic links form a loop, \fItreewalk\fP will not
detect this condition.
.PP
If \fItreewalk\fP detects any error other than EACCES (see \fIFTW_NS\fP,
\fIFTW_DNR\fP, and \fIFTW_CHDIR\fP, above) or EMFILE (in the case of
running out of file descriptors) it returns -1 to its caller, leaving
\fIerrno\fP unchanged.
.SH BUGS
The \fIpath\fP string passed to \fIfunction\fP is the buffer currently
being processed by \fItreewalk\fP and must therefore be copied before
any modifications are made.
.SH HISTORY
The \fItreewalk\fP routine is a superset of the \fIftw\fP routine as
provided by System V.  \fIFtw\fP is available for compatibility.
.SH SEE ALSO
find(1), getdtablesize(2), stat(2), symlink(2), glob(3)