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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" (ignoring symbolic links) or
       physically  (visiting  symbolic links), 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    Re-visit  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 3.24 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				  2007-12-28				FTS(3)
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