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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  corresponding
       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 unde-
       fined 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  possi-
       ble  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 rou-
       tine, 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 .

IEEE/The Open Group                  2003                              FTW(3P)