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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
       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 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 3.25 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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