fts



FTS(3)                    OpenBSD Programmer's Manual                   FTS(3)


NAME

     fts - 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 option);

     int
     fts_close(FTS *ftsp);


DESCRIPTION

     The fts functions are provided for traversing UNIX file hierarchies.  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 within 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'' (following
     symbolic links) or ``physically'' (not following 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 */
             size_t fts_pathlen;             /* strlen(fts_path) */
             char *fts_name;                 /* file name */
             size_t fts_namelen;             /* strlen(fts_name) */
             int 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 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() (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, 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() 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 FTS_PARENTLEVEL (-1), and the FTSENT structure for
                  the root itself is numbered FTS_ROOTLEVEL (0).  Note that
                  while fts_level cannot hold a number of levels greater than
                  FTS_MAXLEVEL, the fts functions themselves are not limited
                  to a fixed number of levels.  Application code that inspects
                  fts_level should be written with this in mind.

     fts_errno    Upon return of an 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 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 NUL 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 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 specified.  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 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 non-existent 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 current
                   directory and try to access files unless FTS_NOCHDIR is
                   specified and absolute pathnames 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, 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 compar argument 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.

     If an error occurs, fts_open() returns NULL and sets errno appropriately.

   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 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(), 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 0.  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.

     options 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 or -1 if an error occurred.  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 the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.


ERRORS

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

     The function fts_close() may fail and set errno for any of the errors
     specified for the library function fchdir(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 specified option is invalid.


SEE ALSO

     find(1), chdir(2), stat(2), qsort(3)


HISTORY

     The fts functions first appeared in 4.3BSD-Reno.  The interface was
     revised in 4.4BSD.

OpenBSD 5.4                      June 5, 2013                      OpenBSD 5.4

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