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FTS(3)		       FreeBSD Library Functions Manual			FTS(3)

NAME
     fts -- traverse a file hierarchy

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <sys/types.h>
     #include <sys/stat.h>
     #include <fts.h>

     FTS *
     fts_open(char * const *path_argv, int options,
	 int (*compar)(const FTSENT * const *, const FTSENT * const *));

     FTSENT *
     fts_read(FTS *ftsp);

     FTSENT *
     fts_children(FTS *ftsp, int options);

     int
     fts_set(FTS *ftsp,	FTSENT *f, int options);

     void
     fts_set_clientptr(FTS *ftsp, void *clientdata);

     void *
     fts_get_clientptr(FTS *ftsp);

     FTS *
     fts_get_stream(FTSENT *f);

     int
     fts_close(FTS *ftsp);

DESCRIPTION
     The fts functions are provided for	traversing UNIX	file hierarchies.  A
     simple overview is	that the fts_open() function returns a ``handle'' on a
     file hierarchy, which is then supplied to the other fts functions.	 The
     function fts_read() returns a pointer to a	structure describing one of
     the files in the file hierarchy.  The function fts_children() returns a
     pointer to	a linked list of structures, each of which describes one of
     the files contained in a directory	in the hierarchy.  In general, direc-
     tories are	visited	two distinguishable times; in pre-order	(before	any of
     their descendants are visited) and	in post-order (after all of their
     descendants have been visited).  Files are	visited	once.  It is possible
     to	walk the hierarchy ``logically'' (ignoring symbolic links) or physi-
     cally (visiting symbolic links), order the	walk of	the hierarchy or prune
     and/or re-visit portions of the hierarchy.

     Two structures are	defined	(and typedef'd)	in the include file <fts.h>.
     The first is FTS, the structure that represents the file hierarchy
     itself.  The second is FTSENT, the	structure that represents a file in
     the file hierarchy.  Normally, an FTSENT structure	is returned for	every
     file in the file hierarchy.  In this manual page, ``file''	and ``FTSENT
     structure'' are generally interchangeable.

     The FTS structure contains	space for a single pointer, which may be used
     to	store application data or per-hierarchy	state.	The
     fts_set_clientptr() and fts_get_clientptr() functions may be used to set
     and retrieve this pointer.	 This is likely	to be useful only when
     accessed from the sort comparison function, which can determine the orig-
     inal FTS stream of	its arguments using the	fts_get_stream() function.
     The two get functions are also available as macros	of the same name.

     The FTSENT	structure contains at least the	following fields, which	are
     described in greater detail below:

     typedef struct _ftsent {
	     u_short fts_info;		     /*	flags for FTSENT structure */
	     char *fts_accpath;		     /*	access path */
	     char *fts_path;		     /*	root path */
	     u_short fts_pathlen;	     /*	strlen(fts_path) */
	     char *fts_name;		     /*	file name */
	     u_short fts_namelen;	     /*	strlen(fts_name) */
	     short fts_level;		     /*	depth (-1 to N)	*/
	     int fts_errno;		     /*	file errno */
	     long fts_number;		     /*	local numeric value */
	     void *fts_pointer;		     /*	local address value */
	     int64_t fts_bignum;	     /*	local 64-bit numeric value */
	     struct ftsent *fts_parent;	     /*	parent directory */
	     struct ftsent *fts_link;	     /*	next file structure */
	     struct ftsent *fts_cycle;	     /*	cycle structure	*/
	     struct stat *fts_statp;	     /*	stat(2)	information */
     } FTSENT;

     These fields are defined as follows:

     fts_info	  One of the following values describing the returned FTSENT
		  structure and	the file it represents.	 With the exception of
		  directories without errors (FTS_D), all of these entries are
		  terminal, that is, they will not be revisited, nor will any
		  of their descendants be visited.

		  FTS_D	       A directory being visited in pre-order.

		  FTS_DC       A directory that	causes a cycle in the tree.
			       (The fts_cycle field of the FTSENT structure
			       will be filled in as well.)

		  FTS_DEFAULT  Any FTSENT structure that represents a file
			       type not	explicitly described by	one of the
			       other fts_info values.

		  FTS_DNR      A directory which cannot	be read.  This is an
			       error return, and the fts_errno field will be
			       set to indicate what caused the error.

		  FTS_DOT      A file named `.'	or `..'	which was not speci-
			       fied as a file name to fts_open() (see
			       FTS_SEEDOT).

		  FTS_DP       A directory being visited in post-order.	 The
			       contents	of the FTSENT structure	will be
			       unchanged from when it was returned in pre-
			       order, i.e., with the fts_info field set	to
			       FTS_D.

		  FTS_ERR      This is an error	return,	and the	fts_errno
			       field will be set to indicate what caused the
			       error.

		  FTS_F	       A regular file.

		  FTS_NS       A file for which	no stat(2) information was
			       available.  The contents	of the fts_statp field
			       are undefined.  This is an error	return,	and
			       the fts_errno field will	be set to indicate
			       what caused the error.

		  FTS_NSOK     A file for which	no stat(2) information was
			       requested.  The contents	of the fts_statp field
			       are undefined.

		  FTS_SL       A symbolic link.

		  FTS_SLNONE   A symbolic link with a non-existent target.
			       The contents of the fts_statp field reference
			       the file	characteristic information for the
			       symbolic	link itself.

     fts_accpath  A path for accessing the file	from the current directory.

     fts_path	  The path for the file	relative to the	root of	the traversal.
		  This path contains the path specified	to fts_open() as a
		  prefix.

     fts_pathlen  The length of	the string referenced by fts_path.

     fts_name	  The name of the file.

     fts_namelen  The length of	the string referenced by fts_name.

     fts_level	  The depth of the traversal, numbered from -1 to N, where
		  this file was	found.	The FTSENT structure representing the
		  parent of the	starting point (or root) of the	traversal is
		  numbered FTS_ROOTPARENTLEVEL (-1), and the FTSENT structure
		  for the root itself is numbered FTS_ROOTLEVEL	(0).

     fts_errno	  Upon return of a FTSENT structure from the fts_children() or
		  fts_read() functions,	with its fts_info field	set to
		  FTS_DNR, FTS_ERR or FTS_NS, the fts_errno field contains the
		  value	of the external	variable errno specifying the cause of
		  the error.  Otherwise, the contents of the fts_errno field
		  are undefined.

     fts_number	  This field is	provided for the use of	the application	pro-
		  gram and is not modified by the fts functions.  It is	ini-
		  tialized to 0.  Note that this field is overlaid by
		  fts_bignum.

     fts_pointer  This field is	provided for the use of	the application	pro-
		  gram and is not modified by the fts functions.  It is	ini-
		  tialized to NULL.  Note that this field is overlaid by
		  fts_bignum.

     fts_bignum	  This field is	provided for the use of	the application	pro-
		  gram and is not modified by the fts functions.  It is	ini-
		  tialized to 0.  Note that this field overlays	fts_number and
		  fts_pointer.

     fts_parent	  A pointer to the FTSENT structure referencing	the file in
		  the hierarchy	immediately above the current file, i.e., the
		  directory of which this file is a member.  A parent struc-
		  ture for the initial entry point is provided as well,	how-
		  ever,	only the fts_level, fts_bignum,	fts_number and
		  fts_pointer fields are guaranteed to be initialized.

     fts_link	  Upon return from the fts_children() function,	the fts_link
		  field	points to the next structure in	the NULL-terminated
		  linked list of directory members.  Otherwise,	the contents
		  of the fts_link field	are undefined.

     fts_cycle	  If a directory causes	a cycle	in the hierarchy (see FTS_DC),
		  either because of a hard link	between	two directories, or a
		  symbolic link	pointing to a directory, the fts_cycle field
		  of the structure will	point to the FTSENT structure in the
		  hierarchy that references the	same file as the current
		  FTSENT structure.  Otherwise,	the contents of	the fts_cycle
		  field	are undefined.

     fts_statp	  A pointer to stat(2) information for the file.

     A single buffer is	used for all of	the paths of all of the	files in the
     file hierarchy.  Therefore, the fts_path and fts_accpath fields are guar-
     anteed to be NUL-terminated only for the file most	recently returned by
     fts_read().  To use these fields to reference any files represented by
     other FTSENT structures will require that the path	buffer be modified
     using the information contained in	that FTSENT structure's	fts_pathlen
     field.  Any such modifications should be undone before further calls to
     fts_read()	are attempted.	The fts_name field is always NUL-terminated.

     Note that the use of fts_bignum is	mutually exclusive with	the use	of
     fts_number	or fts_pointer.

FTS_OPEN
     The fts_open() function takes a pointer to	an array of character pointers
     naming one	or more	paths which make up a logical file hierarchy to	be
     traversed.	 The array must	be terminated by a NULL	pointer.

     There are a number	of options, at least one of which (either FTS_LOGICAL
     or	FTS_PHYSICAL) must be specified.  The options are selected by or'ing
     the following values:

     FTS_COMFOLLOW
		   This	option causes any symbolic link	specified as a root
		   path	to be followed immediately whether or not FTS_LOGICAL
		   is also specified.

     FTS_LOGICAL   This	option causes the fts routines to return FTSENT	struc-
		   tures for the targets of symbolic links instead of the sym-
		   bolic links themselves.  If this option is set, the only
		   symbolic links for which FTSENT structures are returned to
		   the application are those referencing non-existent files.
		   Either FTS_LOGICAL or FTS_PHYSICAL must be provided to the
		   fts_open() function.

     FTS_NOCHDIR   As a	performance optimization, the fts functions change
		   directories as they walk the	file hierarchy.	 This has the
		   side-effect that an application cannot rely on being	in any
		   particular directory	during the traversal.  The FTS_NOCHDIR
		   option turns	off this optimization, and the fts functions
		   will	not change the current directory.  Note	that applica-
		   tions should	not themselves change their current directory
		   and try to access files unless FTS_NOCHDIR is specified and
		   absolute pathnames were provided as arguments to
		   fts_open().

     FTS_NOSTAT	   By default, returned	FTSENT structures reference file char-
		   acteristic information (the statp field) for	each file vis-
		   ited.  This option relaxes that requirement as a perfor-
		   mance optimization, allowing	the fts	functions to set the
		   fts_info field to FTS_NSOK and leave	the contents of	the
		   statp field undefined.

     FTS_PHYSICAL  This	option causes the fts routines to return FTSENT	struc-
		   tures for symbolic links themselves instead of the target
		   files they point to.	 If this option	is set,	FTSENT struc-
		   tures for all symbolic links	in the hierarchy are returned
		   to the application.	Either FTS_LOGICAL or FTS_PHYSICAL
		   must	be provided to the fts_open() function.

     FTS_SEEDOT	   By default, unless they are specified as path arguments to
		   fts_open(), any files named `.' or `..' encountered in the
		   file	hierarchy are ignored.	This option causes the fts
		   routines to return FTSENT structures	for them.

     FTS_XDEV	   This	option prevents	fts from descending into directories
		   that	have a different device	number than the	file from
		   which the descent began.

     The argument compar() specifies a user-defined function which may be used
     to	order the traversal of the hierarchy.  It takes	two pointers to	point-
     ers to FTSENT structures as arguments and should return a negative	value,
     zero, or a	positive value to indicate if the file referenced by its first
     argument comes before, in any order with respect to, or after, the	file
     referenced	by its second argument.	 The fts_accpath, fts_path and
     fts_pathlen fields	of the FTSENT structures may never be used in this
     comparison.  If the fts_info field	is set to FTS_NS or FTS_NSOK, the
     fts_statp field may not either.  If the compar() argument is NULL,	the
     directory traversal order is in the order listed in path_argv for the
     root paths, and in	the order listed in the	directory for everything else.

FTS_READ
     The fts_read() function returns a pointer to an FTSENT structure describ-
     ing a file	in the hierarchy.  Directories (that are readable and do not
     cause cycles) are visited at least	twice, once in pre-order and once in
     post-order.  All other files are visited at least once.  (Hard links
     between directories that do not cause cycles or symbolic links to sym-
     bolic links may cause files to be visited more than once, or directories
     more than twice.)

     If	all the	members	of the hierarchy have been returned, fts_read()
     returns NULL and sets the external	variable errno to 0.  If an error
     unrelated to a file in the	hierarchy occurs, fts_read() returns NULL and
     sets errno	appropriately.	If an error related to a returned file occurs,
     a pointer to an FTSENT structure is returned, and errno may or may	not
     have been set (see	fts_info).

     The FTSENT	structures returned by fts_read() may be overwritten after a
     call to fts_close() on the	same file hierarchy stream, or,	after a	call
     to	fts_read() on the same file hierarchy stream unless they represent a
     file of type directory, in	which case they	will not be overwritten	until
     after a call to fts_read()	after the FTSENT structure has been returned
     by	the function fts_read()	in post-order.

FTS_CHILDREN
     The fts_children()	function returns a pointer to an FTSENT	structure
     describing	the first entry	in a NULL-terminated linked list of the	files
     in	the directory represented by the FTSENT	structure most recently
     returned by fts_read().  The list is linked through the fts_link field of
     the FTSENT	structure, and is ordered by the user-specified	comparison
     function, if any.	Repeated calls to fts_children() will recreate this
     linked list.

     As	a special case,	if fts_read() has not yet been called for a hierarchy,
     fts_children() will return	a pointer to the files in the logical direc-
     tory specified to fts_open(), i.e., the arguments specified to
     fts_open().  Otherwise, if	the FTSENT structure most recently returned by
     fts_read()	is not a directory being visited in pre-order, or the direc-
     tory does not contain any files, fts_children() returns NULL and sets
     errno to zero.  If	an error occurs, fts_children()	returns	NULL and sets
     errno appropriately.

     The FTSENT	structures returned by fts_children() may be overwritten after
     a call to fts_children(), fts_close() or fts_read() on the	same file
     hierarchy stream.

     Option may	be set to the following	value:

     FTS_NAMEONLY  Only	the names of the files are needed.  The	contents of
		   all the fields in the returned linked list of structures
		   are undefined with the exception of the fts_name and
		   fts_namelen fields.

FTS_SET
     The function fts_set() allows the user application	to determine further
     processing	for the	file f of the stream ftsp.  The	fts_set() function
     returns 0 on success, and -1 if an	error occurs.  Option must be set to
     one of the	following values:

     FTS_AGAIN	   Re-visit the	file; any file type may	be re-visited.	The
		   next	call to	fts_read() will	return the referenced file.
		   The fts_stat	and fts_info fields of the structure will be
		   reinitialized at that time, but no other fields will	have
		   been	changed.  This option is meaningful only for the most
		   recently returned file from fts_read().  Normal use is for
		   post-order directory	visits,	where it causes	the directory
		   to be re-visited (in	both pre and post-order) as well as
		   all of its descendants.

     FTS_FOLLOW	   The referenced file must be a symbolic link.	 If the	refer-
		   enced file is the one most recently returned	by fts_read(),
		   the next call to fts_read() returns the file	with the
		   fts_info and	fts_statp fields reinitialized to reflect the
		   target of the symbolic link instead of the symbolic link
		   itself.  If the file	is one of those	most recently returned
		   by fts_children(), the fts_info and fts_statp fields	of the
		   structure, when returned by fts_read(), will	reflect	the
		   target of the symbolic link instead of the symbolic link
		   itself.  In either case, if the target of the symbolic link
		   does	not exist the fields of	the returned structure will be
		   unchanged and the fts_info field will be set	to FTS_SLNONE.

		   If the target of the	link is	a directory, the pre-order
		   return, followed by the return of all of its	descendants,
		   followed by a post-order return, is done.

     FTS_SKIP	   No descendants of this file are visited.  The file may be
		   one of those	most recently returned by either
		   fts_children() or fts_read().

FTS_CLOSE
     The fts_close() function closes a file hierarchy stream ftsp and restores
     the current directory to the directory from which fts_open() was called
     to	open ftsp.  The	fts_close() function returns 0 on success, and -1 if
     an	error occurs.

ERRORS
     The function fts_open() may fail and set errno for	any of the errors
     specified for the library functions open(2) and malloc(3).

     The function fts_close() may fail and set errno for any of	the errors
     specified for the library functions chdir(2) and close(2).

     The functions fts_read() and fts_children() may fail and set errno	for
     any of the	errors specified for the library functions chdir(2),
     malloc(3),	opendir(3), readdir(3) and stat(2).

     In	addition, fts_children(), fts_open() and fts_set() may fail and	set
     errno as follows:

     [EINVAL]		The options were invalid.

SEE ALSO
     find(1), chdir(2),	stat(2), ftw(3), qsort(3)

HISTORY
     The fts interface was first introduced in 4.4BSD.	The
     fts_get_clientptr(), fts_get_stream(), and	fts_set_clientptr() functions
     were introduced in	FreeBSD	5.0, principally to provide for	alternative
     interfaces	to the fts functionality using different data structures.

FreeBSD	9.2			January	7, 2005			   FreeBSD 9.2

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | FTS_OPEN | FTS_READ | FTS_CHILDREN | FTS_SET | FTS_CLOSE | ERRORS | SEE ALSO | HISTORY

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