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FTW(3)			   Linux Programmer's Manual			FTW(3)

NAME
       ftw, nftw - file	tree walk

SYNOPSIS
       #include	<ftw.h>

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

       #define _XOPEN_SOURCE 500   /* See feature_test_macros(7) */
       #include	<ftw.h>

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

DESCRIPTION
       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  de-
       fault, directories are handled before the files and subdirectories they
       contain (preorder traversal).

       To avoid	using up  all  of  the	calling	 process's  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
       tree.

       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,
       and is expressed	either as a pathname relative to the calling process's
       current working directory at the	time of	the call to ftw(), if  dirpath
       was  expressed  as  a relative pathname,	or as an absolute pathname, if
       dirpath was expressed as	an absolute pathname.  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.

       FTW_DNR
	      fpath is a directory which can't be read.

       FTW_NS The stat(2) call failed on fpath,	which is not a symbolic	 link.
	      The  probable cause for this is that the caller had read permis-
	      sion on the parent directory, so that the	filename  fpath	 could
	      be  seen,	 but did not have execute permission, so that the file
	      could not	be reached for stat(2).

	      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 nonzero 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 nonzero 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().   Don't use
       longjmp(3) unless the program is	going to terminate.

   nftw()
       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
       flags:

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

	      FTW_CONTINUE
		     Instructs nftw() to continue normally.

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

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

	      FTW_STOP
		     Causes nftw() to return immediately with the return value
		     FTW_STOP.

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

	      The  feature  test macro _GNU_SOURCE must	be defined (before in-
	      cluding any header files)	in order to obtain the	definition  of
	      FTW_ACTIONRETVAL from _ftw.h_.

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

       FTW_DEPTH
	      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.)

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

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

	      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.  (If
	      FTW_DEPTH	was not	specified in flags, then directories will  al-
	      ways  be	visited	with typeflag set to FTW_D.)  All of the files
	      and subdirectories within	fpath have been	processed.

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

       FTW_SLN
	      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).

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

       If fn() returns nonzero,	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().

VERSIONS
       nftw() is available under glibc since version 2.1.

CONFORMING TO
       POSIX.1-2001, SVr4, SUSv1.  POSIX.1-2008	marks ftw() as obsolete.

NOTES
       POSIX.1-2001  note that the results are unspecified if fn does not pre-
       serve the current working directory.

       The function nftw() and the use of FTW_SL with ftw() were introduced in
       SUSv1.

       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().

       FTW_F is	returned for all objects (files, symbolic links, FIFOs,	 etc.)
       that can	be stat'ed but are not a directory.

       FTW_ACTIONRETVAL	is glibc-specific.

EXAMPLE
       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
       nftw().

   Program source
       #define _XOPEN_SOURCE 500
       #include	<ftw.h>
       #include	<stdio.h>
       #include	<stdlib.h>
       #include	<string.h>
       #include	<stdint.h>

       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 */
       }

       int
       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) {
	       perror("nftw");
	       exit(EXIT_FAILURE);
	   }
	   exit(EXIT_SUCCESS);
       }

SEE ALSO
       stat(2),	fts(3),	readdir(3)

COLOPHON
       This page is part of release 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2014-08-19				FTW(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | VERSIONS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON

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