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FTS(3)			 BSD Library Functions Manual			FTS(3)

NAME
     fts, fts_open, fts_read, fts_children, fts_set, fts_close -- 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 FTSENT **));

     FTSENT *
     fts_read(FTS *ftsp);

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

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

     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 de-
     scendants have been visited).  Files are visited once.  It	is possible to
     walk the hierarchy	"logically" (ignoring symbolic links) or physically
     (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	it-
     self.  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 FTSENT structure contains
     at	least the following fields, which are described	in greater detail be-
     low:

       typedef struct _ftsent {
	       u_short fts_info;	       /* flags	for FTSENT structure */
	       char *fts_accpath;	       /* access path */
	       char *fts_path;		       /* root path */
	       short fts_pathlen;	       /* strlen(fts_path) */
	       char *fts_name;		       /* file name */
	       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 */
	       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 flags 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	un-
			       changed 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 re-
			       quested.	 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_W	       A whiteout object.

     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 -1, and the FTSENT structure	for the	root itself is
		  numbered 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.

     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.

     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_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 NULL-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 us-
     ing 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 NULL-terminated.

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
		     structures	for the	targets	of symbolic links instead of
		     the symbolic links	themselves.  If	this option is set,
		     the only symbolic links for which FTSENT structures are
		     returned to the application are those referencing non-ex-
		     istent 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 applications should not themselves change their
		     current directory and try to access files unless
		     FTS_NOCHDIR is specified and absolute pathnames were pro-
		     vided as arguments	to fts_open().

     FTS_NOSTAT	     By	default, returned FTSENT structures reference file
		     characteristic information	(the statp field) for each
		     file visited.  This option	relaxes	that requirement as a
		     performance 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
		     structures	for symbolic links themselves instead of the
		     target files they point to.  If this option is set,
		     FTSENT structures 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_WHITEOUT    Return whiteout entries, which are	normally hidden.

     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 be-
     tween directories that do not cause cycles	or symbolic links to symbolic
     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()	re-
     turns NULL	and sets the external variable errno to	0.  If an error	unre-
     lated 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 de-
     scribing 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 func-
     tion, 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 hi-
     erarchy 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 re-
     turns 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 ref-
		     erenced 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), qsort(3), symlink(7)

STANDARDS
     The fts utility was expected to be	included in the	IEEE Std 1003.1-1988
     ("POSIX.1") revision.  But	twenty years later, it still was not included
     in	the IEEE Std 1003.1-2008 ("POSIX.1") revision.

BSD				March 30, 2011				   BSD

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

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