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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" (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
                               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 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
                               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  -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
                   program and is not modified 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 modified by the fts  functions.   It  is
                   initialized 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
                   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
       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 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 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
                    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  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
                    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_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
       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    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
                    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 3.24 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/.