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FTW(3)			   Linux Programmers Manual		       FTW(3)

       ftw, nftw - file tree walk


       int ftw(const char *dirpath,
	       int (*fn) (const char *fpath, const struct stat *sb,
			  int typeflag),
	       int nopenfd);

       #define _XOPEN_SOURCE 500

       int nftw(const char *dirpath,
	       int (*fn) (const char *fpath, const struct stat *sb,
			  int typeflag, struct FTW *ftwbuf),
	       int nopenfd, int flags);

       ftw() walks through the directory tree that is located under the direc
       tory dirpath, and calls fn() once for  each  entry  in  the  tree.   By
       default,  directories  are  handled before the files and subdirectories
       they contain (pre-order traversal).

       To avoid using up  all  of  the	calling  processs  file  descriptors,
       nopenfd	specifies  the	maximum  number of directories that ftw() will
       hold open simultaneously.  When the search depth  exceeds  this,  ftw()
       will  become slower because directories have to be closed and reopened.
       ftw() uses at most one file descriptor for each level in the  directory

       For  each  entry  found	in the tree, ftw() calls fn() with three argu
       ments: fpath, sb, and typeflag.	fpath is the  pathname	of  the  entry
       relative to dirpath.  sb is a pointer to the stat structure returned by
       a call to stat(2) for fpath.  typeflag is an integer that  has  one  of
       the following values:

       FTW_F  fpath is a regular file.

       FTW_D  fpath is a directory.

	      fpath is a directory which cant be read.

       FTW_NS The  stat(2) call failed on fpath, which is not a symbolic link.

	      If fpath is a symbolic link  and	stat(2)  failed,  POSIX.1-2001
	      states that it is undefined whether FTW_NS or FTW_SL (see below)
	      is passed in typeflag.

       To stop the tree walk, fn() returns a non-zero value; this  value  will
       become  the  return  value  of ftw().  As long as fn() returns 0, ftw()
       will continue either until it has traversed the entire tree,  in  which
       case  it  will  return zero, or until it encounters an error (such as a
       malloc(3) failure), in which case it will return -1.

       Because ftw() uses dynamic data structures, the only safe way  to  exit
       out of a tree walk is to return a non-zero value from fn().  To allow a
       signal to terminate the walk without causing a memory  leak,  have  the
       handler	set  a	global	flag  that  is	checked  by  fn().   Dont use
       longjmp(3) unless the program is going to terminate.

       The function nftw() is the same as ftw(), except that it has one  addi
       tional  argument, flags, and calls fn() with one more argument, ftwbuf.

       This flags argument is formed by ORing zero or more  of	the  following

       FTW_ACTIONRETVAL (since glibc 2.3.3)
	      If  this	glibc-specific	flag  is  set, then nftw() handles the
	      return value from fn() differently.  fn() should return  one  of
	      the following values:

		     Instructs nftw() to continue normally.

		     If  fn() returns this value, then siblings of the current
		     entry will be skipped, and processing  continues  in  the

		     If  fn()  is  called  with  an  entry that is a directory
		     (typeflag is  FTW_D),  this  return  value  will  prevent
		     objects  within that directory from being passed as argu
		     ments to fn().  nftw() continues processing with the next
		     sibling of the directory.

		     Causes nftw() to return immediately with the return value

	      Other return values could be associated with new actions in  the
	      future;  fn()  should  not return values other than those listed

	      The feature test macro _GNU_SOURCE must be defined in  order  to
	      obtain the definition of FTW_ACTIONRETVAL from .

	      If set, do a chdir(2) to each directory before handling its con
	      tents.  This is useful if the  program  needs  to  perform  some
	      action in the directory in which fpath resides.

	      If  set,	do  a post-order traversal, that is, call fn() for the
	      directory itself after handling the contents  of	the  directory
	      and  its subdirectories.	(By default, each directory is handled
	      before its contents.)

	      If set, stay within the same file system	(i.e.,	do  not  cross
	      mount points).

	      If  set, do not follow symbolic links.  (This is what you want.)
	      If not set, symbolic links are followed, but no file is reported

	      If  FTW_PHYS is not set, but FTW_DEPTH is set, then the function
	      fn() is never called for a directory that would be a  descendant
	      of itself.

       For each entry in the directory tree, nftw() calls fn() with four argu
       ments.  fpath and sb are as for ftw().  typeflag may receive any of the
       same values as with ftw(), or any of the following values:

       FTW_DP fpath is a directory, and FTW_DEPTH was specified in flags.  All
	      of the files and subdirectories  within  fpath  have  been  pro

       FTW_SL fpath is a symbolic link, and FTW_PHYS was set in flags.

	      fpath  is a symbolic link pointing to a nonexistent file.  (This
	      occurs only if FTW_PHYS is not set.)

       The fourth argument that nftw() supplies when calling fn() is a	struc
       ture of type FTW:

	   struct FTW {
	       int base;
	       int level;

       base  is  the  offset of the filename (i.e., basename component) in the
       pathname given in fpath.  level is the depth of fpath in the  directory
       tree, relative to the root of the tree (dirpath, which has depth 0).

       These functions return 0 on success, and -1 if an error occurs.

       If  fn()  returns  non-zero,  then  the tree walk is terminated and the
       value returned by fn() is returned as the result of ftw() or nftw().

       If nftw() is called with the FTW_ACTIONRETVAL flag, then the only  non-
       zero  value  that  should be used by fn() to terminate the tree walk is
       FTW_STOP, and that value is returned as the result of nftw().

       POSIX.1-2001, SVr4, SUSv1.

       The function nftw() and the use of FTW_SL with ftw() were introduced in

       On  some  systems  ftw() will never use FTW_SL, on other systems FTW_SL
       occurs only for symbolic links that do not point to an  existing  file,
       and  again  on  other  systems  ftw() will use FTW_SL for each symbolic
       link.  For predictable control, use nftw().

       Under Linux, libc4 and libc5 and glibc 2.0.6 will  use  FTW_F  for  all
       objects	(files,  symbolic links, FIFOs, etc.)  that can be stated but
       are not a directory.

       The function nftw() is available since glibc 2.1.

       FTW_ACTIONRETVAL is glibc-specific.

       The following program traverses the directory tree under the path named
       in  its	first command-line argument, or under the current directory if
       no argument is supplied.  It displays various  information  about  each
       file.   The second command-line argument can be used to specify charac
       ters that control the value assigned to the flags argument when calling

       #define _XOPEN_SOURCE 500

       static int
       display_info(const char *fpath, const struct stat *sb,
		    int tflag, struct FTW *ftwbuf)
	   printf("%-3s %2d %7jd   %-40s %d %s\n",
	       (tflag == FTW_D) ?   "d"   : (tflag == FTW_DNR) ? "dnr" :
	       (tflag == FTW_DP) ?  "dp"  : (tflag == FTW_F) ?	 "f" :
	       (tflag == FTW_NS) ?  "ns"  : (tflag == FTW_SL) ?  "sl" :
	       (tflag == FTW_SLN) ? "sln" : "???",
	       ftwbuf->level, (intmax_t) sb->st_size,
	       fpath, ftwbuf->base, fpath + ftwbuf->base);
	   return 0;	       /* To tell nftw() to continue */

       main(int argc, char *argv[])
	   int flags = 0;

	   if (argc > 2 && strchr(argv[2], 'd') != NULL)
	       flags |= FTW_DEPTH;
	   if (argc > 2 && strchr(argv[2], 'p') != NULL)
	       flags |= FTW_PHYS;

	   if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags)
		   == -1) {

       stat(2), fts(3), readdir(3), feature_test_macros(7)

       This  page  is  part of release 3.05 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux				  2007-07-26				FTW(3)

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