Unix/Linux Go Back    


Linux 2.6 - man page for fts_read (linux section 3)

Linux & Unix Commands - Search Man Pages
Man Page or Keyword Search:   man
Select Man Page Set:       apropos Keyword Search (sections above)


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 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, 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 physi-
       cally (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 struc-
       ture  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 fol-
       lowing 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 specified as  a  filename
			       to fts_open() (see FTS_SEEDOT).

		   FTS_DP      A  directory  being  visited  in  postorder.   The contents of the
			       FTSENT structure will be unchanged from when it	was  returned  in
			       preorder, 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  con-
			       tents  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 con-
			       tents 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 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  con-
		   tains 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()  func-
		   tions,  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 program and is not modi-
		   fied by the fts functions.  It is initialized to 0.

       fts_pointer This field is provided for the use of the application program and is not modi-
		   fied by the fts functions.  It is initialized to NULL.

       fts_parent  A pointer to the FTSENT structure referencing the file in the hierarchy  imme-
		   diately 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.  Oth-
		   erwise, 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 direc-
		   tory, 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 struc-
		   ture.  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 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 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 ter-
       minated 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 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  tar-
		    gets  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 nonexistent 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  them-
		    selves  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 characteristic informa-
		    tion (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 pro-
		    vided 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 differ-
		    ent 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 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 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_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 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  pos-
		    torder) as well as all of its descendants.

       FTS_FOLLOW   The  referenced  file must be a symbolic link.  If the referenced 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_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 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), 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.

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 3.55 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)
Unix & Linux Commands & Man Pages : ©2000 - 2018 Unix and Linux Forums


All times are GMT -4. The time now is 02:51 AM.