NFTW(3P)                                            POSIX Programmer's Manual                                           NFTW(3P)



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       nftw - walk a file tree

SYNOPSIS
       #include <ftw.h>

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


DESCRIPTION
       The  nftw()  function shall recursively descend the directory hierarchy rooted in path. The nftw() function has a similar
       effect to ftw() except that it takes an additional argument flags, which is a bitwise-inclusive OR of zero or more of the
       following flags:

       FTW_CHDIR
              If set, nftw() shall change the current working directory to each directory as it reports files in that directory.
              If clear, nftw() shall not change the current working directory.

       FTW_DEPTH
              If set, nftw() shall report all files in a directory before reporting the directory itself. If clear, nftw() shall
              report any directory before reporting the files in that directory.

       FTW_MOUNT
              If  set,  nftw()  shall only report files in the same file system as path. If clear, nftw() shall report all files
              encountered during the walk.

       FTW_PHYS
              If set, nftw() shall perform a physical walk and shall not follow symbolic links.


       If FTW_PHYS is clear and FTW_DEPTH is set, nftw() shall follow links instead of reporting them, but shall not report  any
       directory  that  would  be a descendant of itself. If FTW_PHYS is clear and FTW_DEPTH is clear, nftw() shall follow links
       instead of reporting them, but shall not report the contents of any directory that would be a descendant of itself.

       At each file it encounters, nftw() shall call the user-supplied function fn with four arguments:

        * The first argument is the pathname of the object.

        * The second argument is a pointer to the stat buffer containing information on the object.

        * The third argument is an integer giving additional information. Its value is one of the following:

       FTW_F
              The object is a file.

       FTW_D
              The object is a directory.

       FTW_DP
              The object is a directory and subdirectories have been visited. (This condition shall only occur if the  FTW_DEPTH
              flag is included in flags.)

       FTW_SL
              The object is a symbolic link. (This condition shall only occur if the FTW_PHYS flag is included in flags.)

       FTW_SLN
              The  object  is  a  symbolic  link  that  does not name an existing file.  (This condition shall only occur if the
              FTW_PHYS flag is not included in flags.)

       FTW_DNR
              The object is a directory that cannot be read. The fn function shall not be called for any of its descendants.

       FTW_NS
              The stat() function failed on the object because of lack of appropriate permission.  The stat buffer passed to  fn
              is undefined. Failure of stat() for any other reason is considered an error and nftw() shall return -1.


        * The  fourth argument is a pointer to an FTW structure. The value of base is the offset of the object's filename in the
          pathname passed as the first argument to fn. The value of level indicates depth relative to  the  root  of  the  walk,
          where the root level is 0.

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

       The  argument  depth  sets  the maximum number of file descriptors that shall be used by nftw() while traversing the file
       tree. At most one file descriptor shall be used for each directory level.

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

RETURN VALUE
       The nftw() function shall continue until the first of the following conditions occurs:

        * An invocation of fn shall return a non-zero value, in which case nftw() shall return that value.

        * The  nftw()  function  detects an error other than [EACCES] (see FTW_DNR and FTW_NS above), in which case nftw() shall
          return -1 and set errno to indicate the error.

        * The tree is exhausted, in which case nftw() shall return 0.

ERRORS
       The nftw() function shall fail if:

       EACCES Search permission is denied for any component of path or read permission is denied for path, or fn returns -1  and
              does not reset errno.

       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 nftw() function may fail if:

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

       EMFILE {OPEN_MAX} file descriptors are currently open in the calling process.

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

       ENFILE Too many files are currently open in the system.


       In addition, errno may be set if the function pointed to by fn causes errno to be set.

       The following sections are informative.

EXAMPLES
       The following example walks the /tmp directory and its subdirectories, calling the nftw() function  for  every  directory
       entry, to a maximum of 5 levels deep.


              #include <ftw.h>
              ...
              int nftwfunc(const char *, const struct stat *, int, struct FTW *);


              int nftwfunc(const char *filename, const struct stat *statptr,
                  int fileflags, struct FTW *pfwt)
              {
                  return 0;
              }
              ...
              char *startpath = "/tmp";
              int depth = 5;
              int flags = FTW_CHDIR | FTW_DEPTH | FTW_MOUNT;
              int ret;


              ret = nftw(startpath, nftwfunc, depth, flags);

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       lstat(), opendir(), readdir(), stat(), the Base Definitions volume of IEEE Std 1003.1-2001, <ftw.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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                      NFTW(3P)