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



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

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
                 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 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
       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 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
              resolution 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 aa 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
       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.

       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.1-2017, <ftw.h>, <sys_stat.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                               FTW(3)
