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

NAME
       fts,  fts_open, fts_read, fts_children, fts_set, fts_close - traverse a
       file hierarchy

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 file hierarchies.	A sim‐
       ple  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,
       directories  are visited two distinguishable times; in preorder (before
       any of their descendants are visited) and in postorder  (after  all  of
       their  descendants  have been visited).	Files are visited once.	 It is
       possible to walk the hierarchy "logically"  (visiting  the  files  that
       symbolic	 links	point  to)  or physically (visiting the symbolic links
       themselves), order the walk of the hierarchy or	prune  and/or  revisit
       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 FTSENT structure
       contains	 at least the following fields, which are described in greater
       detail below:

	   typedef struct _ftsent {
	       unsigned 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;	    /* filename */
	       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 preorder.

		   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 filename to fts_open() (see FTS_SEE‐
			       DOT).

		   FTS_DP      A directory being visited  in  postorder.   The
			       contents	  of  the  FTSENT  structure  will  be
			       unchanged from when it  was  returned  in  pre‐
			       order,  that is, 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 nonexistent target.  The
			       contents	 of  the fts_statp field reference the
			       file characteristic information	for  the  sym‐
			       bolic 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 traver‐
		   sal.	 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, that is,
		   the directory of which this file is	a  member.   A	parent
		   structure  for the initial entry point is provided as well,
		   however, 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 directo‐
		   ries, 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
       guaranteed 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  buf‐
       fer  be	modified using the information contained in that FTSENT struc‐
       ture'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 point‐
       ers  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_LOGI‐
       CAL  or	FTS_PHYSICAL)  must be specified.  The options are selected by
       ORing 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 nonexis‐
		    tent  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  cur‐
		    rent  directory and try to access files unless FTS_NOCHDIR
		    is specified and absolute pathnames were provided as argu‐
		    ments 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 per‐
		    formance 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_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
       pointers 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
       describing a file in the hierarchy.  Directories (that are readable and
       do  not	cause cycles) are visited at least twice, once in preorder and
       once in postorder.  All other files are visited at least	 once.	 (Hard
       links between directories that do not cause cycles or symbolic links to
       symbolic links may cause files to be visited more than once, or	direc‐
       tories 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 postorder.

   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_chil‐
       dren() will recreate this linked list.

       As  a special case, if fts_read() has not yet been called for a hierar‐
       chy, fts_children() will return a pointer to the files in  the  logical
       directory  specified to fts_open(), that is, the arguments specified to
       fts_open().  Otherwise, if the FTSENT structure most recently  returned
       by  fts_read()  is  not	a  directory being visited in preorder, or the
       directory 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    Revisit the file; any file type  may  be  revisited.   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
		    postorder directory visits, where it causes the  directory
		    to	be  revisited (in both preorder and postorder) 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  preorder
		    return,  followed by the return of all of its descendants,
		    followed by a postorder 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_chil‐
		    dren() 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  suc‐
       cess, and -1 if an error occurs.

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

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

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

VERSIONS
       These functions are available in Linux since glibc2.

CONFORMING TO
       4.4BSD.

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

COLOPHON
       This page is part of release 3.54 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				  2012-10-25				FTS(3)
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