ftw(3C)                        DG/UX R4.11MU05                       ftw(3C)


NAME
       ftw, nftw - walk a file tree

SYNOPSIS
       #include <ftw.h>

       int ftw (const char *path, int (*fn) (const char *, const struct
           stat *, int), int depth);

       int nftw (const char *path, int (*fn) (const char *, const struct
           stat *, int, struct FTW*), int depth, int flags);

DESCRIPTION
       ftw recursively descends the directory hierarchy rooted in path.  For
       each object in the hierarchy, ftw calls the user-defined function fn,
       passing it a pointer to a null-terminated character string containing
       the name of the object, a pointer to a stat structure (see stat(2))
       containing information about the object, and an integer.  Possible
       values of the integer, defined in the ftw.h header file, are:

       FTWF       The object is a file.

       FTWD       The object is a directory.

       FTWDNR     The object is a directory that cannot be read.
                   Descendants of the directory will not be processed.

       FTWNS      stat failed on the object because of lack of appropriate
                   permission or the object is a symbolic link that points
                   to a non-existent file. The stat buffer passed to fn is
                   undefined.

       ftw visits a directory before visiting any of its descendants.

       The tree traversal continues until the tree is exhausted, an
       invocation of fn returns a nonzero value, or some error is detected
       within ftw (such as an I/O error).  If the tree is exhausted, ftw
       returns zero.  If fn returns a nonzero value, ftw stops its tree
       traversal and returns whatever value was returned by fn.  If ftw
       detects an error other than EACCES, it returns -1, and sets the error
       type in errno.

       The function nftw is similar to ftw except that it takes an
       additional argument, flags.  The flags field is used to specify:

       FTWPHYS    Physical walk, does not follow symbolic links.
                   Otherwise, nftw will follow links but will not walk down
                   any path that crosses itself.

       FTWMOUNT   The walk will not cross a mount point.

       FTWDEPTH   All subdirectories will be visited before the directory
                   itself.

       FTWCHDIR   The walk will change to each directory before reading it.

       The function nftw calls fn with four arguments at each file and
       directory.  The first argument is the pathname of the object, the
       second is a pointer to the stat buffer, the third is an integer
       giving additional information, and the fourth is a struct FTW that
       contains the following members:
            int base;
            int level;
       base is the offset into the pathname of the base name of the object.
       level indicates the depth relative to the rest of the walk, where the
       root level is zero.

       The values of the third argument are as follows:

       FTWF       The object is a file.

       FTWD       The object is a directory.

       FTWDP      The object is a directory and subdirectories have been
                   visited.

       FTWSLN     The object is a symbolic link that points to a non-
                   existent file.

       FTWDNR     The object is a directory that cannot be read.  fn will
                   not be called for any of its descendants.

       FTWNS      stat failed on the object because of lack of appropriate
                   permission.  The stat buffer passed to fn is undefined.
                   stat failure other than lack of appropriate permission
                   (EACCES) is considered an error and nftw will return -1.

       Both ftw and nftw use one file descriptor for each level in the tree.
       The depth argument limits the number of file descriptors so used.  If
       depth is zero or negative, the effect is the same as if it were 1.
       depth must not be greater than the number of file descriptors
       currently available for use.  ftw will run faster if depth is at
       least as large as the number of levels in the tree.  When ftw and
       nftw return, they close any file descriptors they have opened; they
       do not close any file descriptors that may have been opened by fn.


   Considerations for Threads Programming
                     +---------+-----------------------------+
                     |         |                      async- |
                     |function | reentrant   cancel   cancel |
                     |         |             point     safe  |
                     +---------+-----------------------------+
                     |ftw      |     Y         Y        N    |
                     |nftw     |     N         -        -    |
                     +---------+-----------------------------+

SEE ALSO
       stat(2), reentrant(3), malloc(3C).

NOTES
       Because ftw is recursive, it is possible for it to terminate with a
       memory fault when applied to very deep file structures.

       ftw uses malloc(3C) to allocate dynamic storage during its operation.
       If ftw is forcibly terminated, such as by longjmp being executed by
       fn or an interrupt routine, ftw will not have a chance to free that
       storage, so it will remain permanently allocated.  A safe way to
       handle interrupts is to store the fact that an interrupt has
       occurred, and arrange to have fn return a nonzero value at its next
       invocation.


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