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Linux 2.6 - man page for ftw (linux section 3posix)

FTW(P)				    POSIX Programmer's Manual				   FTW(P)

       ftw - traverse (walk) a file tree

       #include <ftw.h>

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

       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.

	      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 descrip-
       tors 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.

       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.

       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.

	      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.

	      A component of path is not a directory.

	      A field in the stat structure cannot be represented correctly in the  current  pro-
	      gramming 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.

	      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

       The following sections are informative.

   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);

       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 stor-
       age, 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.



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

       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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					   FTW(P)

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