NFTW(3)                    POSIX Programmer's Manual                   NFTW(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
       nftw -- walk a file tree

SYNOPSIS
       #include <ftw.h>

       int nftw(const char *path, int (*fn)(const char *,
           const struct stat *, int, struct FTW *), int fd__limit, int flags);

DESCRIPTION
       The nftw() function shall recursively descend the directory hierarchy
       rooted in path.  The nftw() function has a similar effect to ftw()
       except that it takes an additional argument flags, which is a bitwise-
       inclusive OR of zero or more of the following flags:

       FTW_CHDIR   If set, nftw() shall change the current working directory
                   to each directory as it reports files in that directory. If
                   clear, nftw() shall not change the current working
                   directory.

       FTW_DEPTH   If set, nftw() shall report all files in a directory before
                   reporting the directory itself. If clear, nftw() shall
                   report any directory before reporting the files in that
                   directory.

       FTW_MOUNT   If set, nftw() shall only report files in the same file
                   system as path.  If clear, nftw() shall report all files
                   encountered during the walk.

       FTW_PHYS    If set, nftw() shall perform a physical walk and shall not
                   follow symbolic links.

       If FTW_PHYS is clear and FTW_DEPTH is set, nftw() shall follow links
       instead of reporting them, but shall not report any directory that
       would be a descendant of itself. If FTW_PHYS is clear and FTW_DEPTH is
       clear, nftw() shall follow links instead of reporting them, but shall
       not report the contents of any directory that would be a descendant of
       itself.

       At each file it encounters, nftw() shall call the user-supplied
       function fn with four arguments:

        *  The first argument is the pathname of the object.

        *  The second argument is a pointer to the stat buffer containing
           information on the object, filled in as if fstatat(), stat(), or
           lstat() had been called to retrieve the information.

        *  The third argument is an integer giving additional information. Its
           value is one of the following:

           FTW_D     The object is a directory.

           FTW_DNR   The object is a directory that cannot be read. The fn
                     function shall not be called for any of its descendants.

           FTW_DP    The object is a directory and subdirectories have been
                     visited. (This condition shall only occur if the
                     FTW_DEPTH flag is included in flags.)

           FTW_F     The object is a non-directory file.

           FTW_NS    The stat() function failed on the object because of lack
                     of appropriate permission. The stat buffer passed to fn
                     is undefined. Failure of stat() for any other reason is
                     considered an error and nftw() shall return -1.

           FTW_SL    The object is a symbolic link. (This condition shall only
                     occur if the FTW_PHYS flag is included in flags.)

           FTW_SLN   The object is a symbolic link that does not name an
                     existing file.  (This condition shall only occur if the
                     FTW_PHYS flag is not included in flags.)

        *  The fourth argument is a pointer to an FTW structure.  The value of
           base is the offset of the object's filename in the pathname passed
           as the first argument to fn.  The value of level indicates depth
           relative to the root of the walk, where the root level is 0.

       The results are unspecified if the application-supplied fn function
       does not preserve the current working directory.

       The argument fd__limit sets the maximum number of file descriptors that
       shall be used by nftw() while traversing the file tree. At most one
       file descriptor shall be used for each directory level.

       The nftw() function need not be thread-safe.

RETURN VALUE
       The nftw() function shall continue until the first of the following
       conditions occurs:

        *  An invocation of fn shall return a non-zero value, in which case
           nftw() shall return that value.

        *  The nftw() function detects an error other than [EACCES] (see
           FTW_DNR and FTW_NS above), in which case nftw() shall return -1 and
           set errno to indicate the error.

        *  The tree is exhausted, in which case nftw() shall return 0.

ERRORS
       The nftw() function shall fail if:

       EACCES Search permission is denied for any component of path or read
              permission is denied for path, or fn returns -1 and does not
              reset errno.

       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 nftw() function may fail if:

       ELOOP  More than {SYMLOOP_MAX} symbolic links were encountered during
              resolution of the path argument.

       EMFILE All file descriptors available to the process are currently
              open.

       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}.

       ENFILE Too many files are currently open in the system.

       In addition, errno may be set if the function pointed to by fn causes
       errno to be set.

       The following sections are informative.

EXAMPLES
       The following program traverses the directory tree under the path named
       in its first command-line argument, or under the current directory if
       no argument is supplied. It displays various information about each
       file. The second command-line argument can be used to specify
       characters that control the value assigned to the flags argument when
       calling nftw().


           #include <ftw.h>
           #include <stdio.h>
           #include <stdlib.h>
           #include <string.h>
           #include <stdint.h>

           static int
           display_info(const char *fpath, const struct stat *sb,
               int tflag, struct FTW *ftwbuf)
           {
               printf("%-3s %2d %7jd   %-40s %d %s\n",
                   (tflag == FTW_D) ?   "d"   : (tflag == FTW_DNR) ? "dnr" :
                   (tflag == FTW_DP) ?  "dp"  : (tflag == FTW_F) ?
                       (S_ISBLK(sb->st_mode) ? "f b" :
                        S_ISCHR(sb->st_mode) ? "f c" :
                        S_ISFIFO(sb->st_mode) ? "f p" :
                        S_ISREG(sb->st_mode) ? "f r" :
                        S_ISSOCK(sb->st_mode) ? "f s" : "f ?") :
                   (tflag == FTW_NS) ?  "ns"  : (tflag == FTW_SL) ?  "sl" :
                   (tflag == FTW_SLN) ? "sln" : "?",
                   ftwbuf->level, (intmax_t) sb->st_size,
                   fpath, ftwbuf->base, fpath + ftwbuf->base);
               return 0;           /* To tell nftw() to continue */
           }

           int
           main(int argc, char *argv[])
           {
               int flags = 0;

               if (argc > 2 && strchr(argv[2], 'd') != NULL)
                   flags |= FTW_DEPTH;
               if (argc > 2 && strchr(argv[2], 'p') != NULL)
                   flags |= FTW_PHYS;

               if (nftw((argc < 2) ? "." : argv[1], display_info, 20, flags) == -1)
               {
                   perror("nftw");
                   exit(EXIT_FAILURE);
               }

               exit(EXIT_SUCCESS);
           }

APPLICATION USAGE
       The nftw() function may allocate dynamic storage during its operation.
       If nftw() is forcibly terminated, such as by longjmp() or siglongjmp()
       being executed by the function pointed to by fn or an interrupt
       routine, nftw() 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
       fdopendir(), fstatat(), readdir()

       The Base Definitions volume of POSIX.1-2017, <ftw.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                              NFTW(3)
