NAME

       ftw - traverse (walk) a file tree

SYNOPSIS

       #include <ftw.h>

       int ftw(const char *path, int (*fn)(const char *,
              const struct stat *ptr, int flag), int ndirs);

DESCRIPTION

       The  ftw()  function shall recursively descend the directory hierarchy rooted in path. For
       each object in the hierarchy, ftw() shall call the function pointed to by fn, passing it a
       pointer to a null-terminated character string containing the name of the object, a pointer
       to a stat structure containing information about the object,  and  an  integer.   Possible
       values of the integer, defined in the <ftw.h> header, are:

       FTW_D  For a directory.

       FTW_DNR
              For a directory that cannot be read.

       FTW_F  For a file.

       FTW_SL For a symbolic link (but see also FTW_NS below).

       FTW_NS For  an object other than a symbolic link on which stat() could not successfully be
              executed. If the object is a symbolic link and stat()  failed,  it  is  unspecified
              whether ftw() passes FTW_SL or FTW_NS to the user-supplied function.

       If  the  integer  is FTW_DNR, descendants of that directory shall not be processed. If the
       integer is FTW_NS, the stat structure contains undefined values. An example of  an  object
       that would cause FTW_NS to be passed to the function pointed to by fn would be a file in a
       directory with read but without execute (search) permission.

       The ftw() function shall visit a directory before visiting any of its descendants.

       The ftw() function shall use at most one file descriptor for each level in the tree.

       The argument ndirs should be in the range [1, {OPEN_MAX}].

       The tree traversal shall continue until either the tree is exhausted, an invocation of  fn
       returns a non-zero value, or some error, other than [EACCES], is detected within ftw().

       The  ndirs  argument  shall  specify  the  maximum  number  of  directory  streams or file
       descriptors or both available for use by ftw()  while  traversing  the  tree.  When  ftw()
       returns it shall close any directory streams and file descriptors it uses not counting any
       opened by the application-supplied fn function.

       The results are unspecified if the application-supplied fn function does not preserve  the
       current working directory.

       The  ftw() function need not be reentrant. A function that is not required to be reentrant
       is not required to be thread-safe.

RETURN VALUE

       If the tree is exhausted, ftw() shall return 0. If the function pointed to by fn returns a
       non-zero value, ftw() shall stop its tree traversal and return whatever value was returned
       by the function pointed to by fn. If ftw() detects an error, it shall return  -1  and  set
       errno to indicate the error.

       If  ftw() encounters an error other than [EACCES] (see FTW_DNR and FTW_NS above), it shall
       return -1 and set errno to indicate the error. The external variable errno may contain any
       error  value that is possible when a directory is opened or when one of the stat functions
       is executed on a directory or file.

ERRORS

       The ftw() function shall fail if:

       EACCES Search permission is denied for any component of path or read permission is  denied
              for path.

       ELOOP  A loop exists in symbolic links encountered during resolution of the path argument.

       ENAMETOOLONG
              The  length  of  the  path  argument  exceeds {PATH_MAX} or a pathname component is
              longer than {NAME_MAX}.

       ENOENT A component of path does not name an existing file or path is an empty string.

       ENOTDIR
              A component of path is not a directory.

       EOVERFLOW
              A field in the stat structure  cannot  be  represented  correctly  in  the  current
              programming environment for one or more files found in the file hierarchy.

       The ftw() function may fail if:

       EINVAL The value of the ndirs argument is invalid.

       ELOOP  More  than  {SYMLOOP_MAX}  symbolic links were encountered during resolution of the
              path argument.

       ENAMETOOLONG
              Pathname resolution of a symbolic link produced an intermediate result whose length
              exceeds {PATH_MAX}.

       In  addition,  if the function pointed to by fn encounters system errors, errno may be set
       accordingly.

       The following sections are informative.

EXAMPLES

   Walking a Directory Structure
       The following example walks the current directory structure, calling the fn  function  for
       every directory entry, using at most 10 file descriptors:

              #include <ftw.h>
              ...
              if (ftw(".", fn, 10) != 0) {
                  perror("ftw"); exit(2);
              }

APPLICATION USAGE

       The  ftw()  function  may  allocate  dynamic  storage  during  its operation.  If ftw() is
       forcibly terminated, such as by longjmp() or siglongjmp() being executed by  the  function
       pointed  to  by  fn  or  an  interrupt  routine, ftw() does not have a chance to free that
       storage, so it remains permanently allocated. A safe way to handle interrupts is to  store
       the fact that an interrupt has occurred, and arrange to have the function pointed to by fn
       return a non-zero value at its next invocation.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       longjmp() , lstat() , malloc() , nftw() , opendir() , siglongjmp() ,  stat()  ,  the  Base
       Definitions volume of IEEE Std 1003.1-2001, <ftw.h>, <sys/stat.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at http://www.opengroup.org/unix/online.html .