ftw(3C)                UNIX System V(C Development Set)                 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.



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ftw(3C)                UNIX System V(C Development Set)                 ftw(3C)


      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;













































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ftw(3C)                UNIX System V(C Development Set)                 ftw(3C)


      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.

SEE ALSO
      stat(2), 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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