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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 .