fts_children

       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 */

                   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_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
                    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
       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
                    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 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://man7.org/linux/man-pages/.



Linux                             2007-12-28                            FTS(3)
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