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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 simple overview is that the fts_open() func-
       tion 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  con-
       tained in a directory in the hierarchy.  In general, directories are visited two distinguishable times; in pre-
       order (before any of their descendants are visited) and in post-order (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 re-visit  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 pre-order.

                   FTS_DC      A directory that causes a cycle in the tree.  (The fts_cycle field of the FTSENT struc-
                               ture 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 post-order.  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 refer-
                               ence 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  func-
                   tions.  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 func-
                   tions.  It is initialized to NULL.

       fts_parent  A pointer to the FTSENT structure referencing the file in the hierarchy immediately above the  cur-
                   rent  file, that is, the directory of which this file is a member.  A parent structure for the ini-
                   tial 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 hierar-
                    chy.  This has the side-effect that an application cannot rely on being in any  particular  direc-
                    tory  during the traversal.  The FTS_NOCHDIR option turns off this optimization, and the fts func-
                    tions 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 path-
                    names 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, allow-
                    ing 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  sym-
                    bolic  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 hierar-
       chy.  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 direc-
       tory for everything else.

   fts_read()
       The fts_read() function returns a pointer to an FTSENT structure describing a file in the hierarchy.   Directo-
       ries  (that  are  readable  and  do not cause cycles) are visited at least twice, once in pre-order and once in
       post-order.  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 post-order.

   fts_children()
       The fts_children() function returns a pointer to an FTSENT structure describing the first entry in a  NULL-ter-
       minated 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
       pre-order, 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 re-visited.  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 post-order directory visits,  where  it
                    causes  the  directory to be re-visited (in both pre and post-order) as well as all of its descen-
                    dants.

       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 pre-order return, followed by the return of all of
                    its descendants, followed by a post-order 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 direc-
       tory 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 3.22 of the Linux man-pages project.  A description of the project,  and  informa-
       tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                             2007-12-28                            FTS(3)