nftw


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 direc-
       tory 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 argu-
       ments: 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()
       tional 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  argu-
                     ments 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 con-
              tents.  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 file system  (i.e.,  do  not  cross
              mount points).

       FTW_PHYS
              If  set, do not follow symbolic links.  (This is what you want.)
              of the files and subdirectories  within  fpath  have  been  pro-
              cessed.

       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  struc-
       ture 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  pre-
       serve 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.

       #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 3.35 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://man7.org/linux/man-pages/.



Linux                             2010-09-20                            FTW(3)
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