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

PROLOG

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

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 direc-
       tory 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 tra-
       versal 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 sig-
       longjmp() 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 Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								   FTW(3P)