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FTS(3)                   BSD Library Functions Manual                   FTS(3)

NAME
     fts -- traverse a file hierarchy

LIBRARY
     Standard C Library (libc, -lc)

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 **));

     FTS *
     fts_open_b(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 UNIX file hierarchies.  A simple overview is that the
     fts_open() and fts_open_b() functions return 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 pre-order (before any of their descen-dants descendants
     dants 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 physi-cally physically
     cally (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 struc-ture structure
     ture 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 hier-archy. hierarchy.
     archy.  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 {
             u_short fts_info;               /* flags for FTSENT structure */
             char *fts_accpath;              /* access path */
             char *fts_path;                 /* root path */
             u_short fts_pathlen;            /* strlen(fts_path) */
             char *fts_name;                 /* file name */
             u_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 values describing the returned FTSENT structure and the file it rep-resents. represents.
                  resents.  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 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 file name to fts_open()
                               or fts_open_b() (see FTS_SEEDOT).

                  FTS_DP       A directory being visited in post-order.  The contents of the FTSENT struc-ture structure
                               ture will be unchanged from when it was returned in pre-order, i.e. 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 non-existent 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() or fts_open_b() 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 num-bered numbered
                  bered FTS_ROOTPARENTLEVEL (-1), and the FTSENT structure for the root itself is numbered
                  FTS_ROOTLEVEL (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, i.e. 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 struc-ture structure
                  ture 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 NUL-terminated only for the file most recently
     returned by fts_read().  To use these fields to reference any files represented by other FTSENT struc-tures structures
     tures 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 NUL-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 spec-ified. specified.
     ified.  The options are selected by or'ing the following values:

     FTS_COMFOLLOW    This option causes any symbolic link specified as a root path to be followed immedi-ately immediately
                      ately 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 non-existent files.  Either FTS_LOGICAL or FTS_PHYSICAL must be pro-vided provided
                      vided 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 argu-ments arguments
                      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 perfor-mance performance
                      mance optimization, not calling stat(2) whenever possible.  If stat(2) doesn't need to
                      be called, the fts functions will set the fts_info field to FTS_NSOK; otherwise
                      fts_info will be set to the correct file information value corresponding to the
                      stat(2) information.  In any case, the statp field will always be undefined.  Note
                      that because fts detects directory cycles and dangling symbolic links, stat(2) is
                      always called for directories and is called for symbolic links when FTS_LOGICAL is
                      set.

     FTS_NOSTAT_TYPE  Like FTS_NOSTAT but if the file type is returned by readdir(3), the corresponding file
                      information value is returned in fts_info instead of FTS_NSOK.

     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 compar-ison. comparison.
     ison.  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_OPEN_B
     The fts_open_b() function is like fts_open() except compar is a block pointer instead of a function
     pointer.  This block is passed to qsort_b(3) (whereas fts_open() passes its function pointer to
     qsort(3)).

           Note: The Block_copy() function (defined in <Blocks.h>) is used by fts_open_b() to make a copy of
           the block, especially for the case when a stack-based block might go out of scope when the sub-routine subroutine
           routine returns.

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 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-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 struc-ture, structure,
     ture, 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(), i.e. 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 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 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
     directory from which fts_open() was called to open ftsp.  The fts_close() function returns 0 on suc-cess, success,
     cess, and -1 if an error occurs.

ERRORS
     The function fts_open() may fail and set errno for any of the errors specified for the library func-tions functions
     tions open(2) and malloc(3).

     The function fts_close() may fail and set errno for any of the errors specified for the library func-tions functions
     tions chdir(2) and close(2).

     The functions fts_read() and fts_children() may fail and set errno for any of the errors specified for
     the library functions 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.

SEE ALSO
     find(1), chdir(2), stat(2), qsort(3), qsort_b(3)

STANDARDS
     The fts utility is expected to be included in a future IEEE Std 1003.1-1988 (``POSIX.1'') revision.

BSD                              Sept 24, 2012                             BSD

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