fts_set

       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 */
                   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_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-
                    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

       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-

                    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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