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

PROLOG         top

       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         top

       ftw — traverse (walk) a file tree

SYNOPSIS         top

       #include <ftw.h>

       int ftw(const char *path, int (*fn)(const char *,
           const struct stat *ptr, int flag), int ndirs);

DESCRIPTION         top

       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

       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

       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         top

       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         top

       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.

              The length of a component of a pathname is longer than

       ENOENT A component of path does not name an existing file or path is
              an empty string.

              A component of path names an existing file that is neither a
              directory nor a symbolic link to a directory.

              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.

              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         top

   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

           #include <ftw.h>
           if (ftw(".", fn, 10) != 0) {
               perror("ftw"); exit(2);


       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

       Applications should use the nftw() function instead of the
       obsolescent ftw() function.

RATIONALE         top



       The ftw() function may be removed in a future version.

SEE ALSO         top

       fdopendir(3p), fstatat(3p), longjmp(3p), nftw(3p), siglongjmp(3p)

       The Base Definitions volume of POSIX.1‐2008, ftw.h(0p),

COPYRIGHT         top

       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 Electrical 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 .

       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 .

IEEE/The Open Group                 2013                             FTW(3P)

Pages that refer to this page: ftw.h(0p)