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NAME

       ftw, nftw - file tree walk

SYNOPSIS

       #include <ftw.h>

       int ftw(const char *dirpath,
               int (*fn) (const char *fpath, const struct stat *sb,
                          int typeflag),
               int nopenfd);

       #define _XOPEN_SOURCE 500   /* See feature_test_macros(7) */
       #include <ftw.h>

       int nftw(const char *dirpath,
               int (*fn) (const char *fpath, const struct stat *sb,
                          int typeflag, struct FTW *ftwbuf),
               int nopenfd, int flags);

DESCRIPTION

       ftw()  walks  through the directory tree that is located under the directory dirpath, and calls fn() once
       for each entry in the tree.  By default, directories are handled before the files and subdirectories they
       contain (preorder traversal).

       To  avoid using up all of the calling process's file descriptors, nopenfd specifies the maximum number of
       directories that ftw() will hold open simultaneously.  When the search depth  exceeds  this,  ftw()  will
       become slower because directories have to be closed and reopened.  ftw() uses at most one file descriptor
       for each level in the directory tree.

       For each entry found in the tree, ftw() calls fn() with three arguments: fpath, sb, and typeflag.   fpath
       is  the  pathname  of  the entry, and is expressed either as a pathname relative to the calling process's
       current working directory at the time of the call to ftw(),  if  dirpath  was  expressed  as  a  relative
       pathname,  or as an absolute pathname, if dirpath was expressed as an absolute pathname.  sb is a pointer
       to the stat structure returned by a call to stat(2) for fpath.  typeflag is an integer that  has  one  of
       the following values:

       FTW_F  fpath is a regular file.

       FTW_D  fpath is a directory.

       FTW_DNR
              fpath is a directory which can't be read.

       FTW_NS The stat(2) call failed on fpath, which is not a symbolic link.

              If  fpath  is a symbolic link and stat(2) failed, POSIX.1-2001 states that it is undefined whether
              FTW_NS or FTW_SL (see below) is passed in typeflag.

       To stop the tree walk, fn() returns a nonzero value; this value will become the return  value  of  ftw().
       As  long  as  fn() returns 0, ftw() will continue either until it has traversed the entire tree, in which
       case it will return zero, or until it encounters an error (such as a malloc(3) failure), in which case it
       will return -1.

       Because  ftw()  uses dynamic data structures, the only safe way to exit out of a tree walk is to return a
       nonzero value from fn().  To allow a signal to terminate the walk without causing a memory leak, have the
       handler  set  a global flag that is checked by fn().  Don't use longjmp(3) unless the program is going to
       terminate.

   nftw()
       The function nftw() is the same as ftw(), except that it has one additional argument,  flags,  and  calls
       fn() with one more argument, ftwbuf.

       This flags argument is formed by ORing zero or more of the following flags:

       FTW_ACTIONRETVAL (since glibc 2.3.3)
              If  this  glibc-specific  flag is set, then nftw() handles the return value from fn() differently.
              fn() should return one of the following values:

              FTW_CONTINUE
                     Instructs nftw() to continue normally.

              FTW_SKIP_SIBLINGS
                     If fn() returns this value, then siblings  of  the  current  entry  will  be  skipped,  and
                     processing continues in the parent.

              FTW_SKIP_SUBTREE
                     If  fn() is called with an entry that is a directory (typeflag is FTW_D), this return value
                     will prevent objects within that directory from being passed as arguments to fn().   nftw()
                     continues processing with the next sibling of the directory.

              FTW_STOP
                     Causes nftw() to return immediately with the return value FTW_STOP.

              Other  return  values  could  be associated with new actions in the future; fn() should not return
              values other than those listed above.

              The feature test macro _GNU_SOURCE must be defined (before including any header files) in order to
              obtain the definition of FTW_ACTIONRETVAL from <ftw.h>.

       FTW_CHDIR
              If  set,  do  a  chdir(2)  to  each directory before handling its contents.  This is useful if the
              program needs to perform some action in the directory in which fpath resides.

       FTW_DEPTH
              If set, do a post-order traversal, that is, call fn() for the directory itself after handling  the
              contents  of  the directory and its subdirectories.  (By default, each directory is handled before
              its contents.)

       FTW_MOUNT
              If set, stay within the same filesystem (i.e., do not cross mount points).

       FTW_PHYS
              If set, do not follow symbolic links.  (This is what you want.)  If not set,  symbolic  links  are
              followed, but no file is reported twice.

              If  FTW_PHYS  is  not  set,  but  FTW_DEPTH  is  set, then the function fn() is never called for a
              directory that would be a descendant of itself.

       For each entry in the directory tree, nftw() calls fn() with four arguments.  fpath and  sb  are  as  for
       ftw().  typeflag may receive any of the same values as with ftw(), or any of the following values:

       FTW_DP fpath  is  a directory, and FTW_DEPTH was specified in flags.  All of the files and subdirectories
              within fpath have been processed.

       FTW_SL fpath is a symbolic link, and FTW_PHYS was set in flags.

       FTW_SLN
              fpath is a symbolic link pointing to a nonexistent file.  (This occurs only  if  FTW_PHYS  is  not
              set.)

       The fourth argument that nftw() supplies when calling fn() is a structure of type FTW:

           struct FTW {
               int base;
               int level;
           };

       base  is  the offset of the filename (i.e., basename component) in the pathname given in fpath.  level is
       the depth of fpath in the directory tree, relative to the root of the tree (dirpath, which has depth 0).

RETURN VALUE

       These functions return 0 on success, and -1 if an error occurs.

       If fn() returns nonzero, then the tree walk is terminated and the value returned by fn() is  returned  as
       the result of ftw() or nftw().

       If  nftw()  is  called with the FTW_ACTIONRETVAL flag, then the only nonzero value that should be used by
       fn() to terminate the tree walk is FTW_STOP, and that value is returned as the result of nftw().

CONFORMING TO

       POSIX.1-2001, SVr4, SUSv1.  POSIX.1-2008 marks ftw() as obsolete.

NOTES

       POSIX.1-2001 note that the results are unspecified if fn does not preserve the current working directory.

       The function nftw() and the use of FTW_SL with ftw() were introduced in SUSv1.

       On some systems ftw() will never use FTW_SL, on other systems FTW_SL occurs only for symbolic links  that
       do  not  point  to  an  existing file, and again on other systems ftw() will use FTW_SL for each symbolic
       link.  For predictable control, use nftw().

       Under Linux, libc4 and libc5 and glibc 2.0.6 will use FTW_F  for  all  objects  (files,  symbolic  links,
       FIFOs, etc.)  that can be stat'ed but are not a directory.

       The function nftw() is available since glibc 2.1.

       FTW_ACTIONRETVAL is glibc-specific.

EXAMPLE

       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().

       #define _XOPEN_SOURCE 500
       #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) ?   "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);
       }

SEE ALSO

       stat(2), fts(3), readdir(3)

COLOPHON

       This page is part of release 3.54 of the Linux man-pages project.  A  description  of  the  project,  and
       information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.