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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,  filled  in  as  if
       stat() or lstat() had been called to retrieve the information. 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 non-directory 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 sym-
                 bolic 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 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  a  component  of  a  pathname  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 names an existing file  that  is  neither  a
              directory nor a symbolic link to 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
              The length of a pathname exceeds {PATH_MAX}, or pathname resolu-
              tion  of  a symbolic link produced an intermediate result with a
              length that 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.
       Applications  should use the nftw() function instead of the obsolescent
       ftw() function.
RATIONALE
       None.
FUTURE DIRECTIONS
       The ftw() function may be removed in a future version.
SEE ALSO
       fdopendir(), fstatat(), longjmp(), nftw(), siglongjmp()
       The Base Definitions volume of POSIX.1-2008, <ftw.h>, <sys_stat.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/online.html .
       Any  typographical  or  formatting  errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files  to  man page format. To report such errors, see https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                              FTW(3P)