nftw

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



NAME
       ftw, nftw - file tree walk

SYNOPSIS
       #include <ftw.h>

       int  ftw(const char *dir, int (*fn)(const char *file, const struct stat
       *sb, int flag), int depth);

       int nftw(const char *dir, int (*fn)(const char *file, const struct stat
       *sb, int flag, struct FTW *s), int depth, int flags);

DESCRIPTION
       ftw()  walks  through  the  directory  tree starting from the indicated
       directory dir.  For each found entry in the tree, it  calls  fn()  with
       the  full pathname of the entry, a pointer to the stat(2) structure for
       the entry and an int flag, which value will be one of the following:

       FTW_F  Item is a normal file

       FTW_D  Item is a directory

       FTW_DNR
              Item is a directory which can't be read

       FTW_SL Item is a symbolic link

       FTW_NS The stat failed on the item which is not a symbolic link

       If the item is a symbolic link and stat failed, XPG4v2 states  that  it
       is undefined whether FTW_NS or FTW_SL is used.

       ftw()  recursively  calls itself for traversing found directories, han-
       dling a directory before its files or subdirectories.  To  avoid  using
       up  all a program's file descriptors, the depth specifies the number of
       simultaneous open directories.  When the depth is exceeded, ftw()  will
       become slower because directories have to be closed and reopened. ftw()
       uses at most one file descriptor for each level in the file  hierarchy.

       To  stop  the tree walk, fn() returns a non-zero value; this value will
       become the return value of ftw().  Otherwise, ftw() will continue until
       it has traversed the entire tree, in which case it will return zero, or
       until it hits an error other than EACCES (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 non-zero  value.   To  handle  inter-
       rupts,  for example, mark that the interrupt occurred and return a non-
       zero value¿don't use longjmp(3) unless the program is going  to  termi-
       nate.

       The  function  nftw()  does precisely the same as ftw(), except that it
       has one additional argument flags (and calls the supplied function with
       one  more  argument).   This flags argument is an OR of zero or more of
       the following flags:

       FTW_CHDIR
              If set, do a chdir() to each directory before handling its  con-
              tents.

       FTW_DEPTH
              If  set, do a depth-first search, that is, call the function for
              the directory itself only after handling  the  contents  of  the
              directory and its subdirectories.

       FTW_MOUNT
              If set, stay within the same file system.

       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.

       The function fn() is called with four arguments: the  pathname  of  the
       reported  entry,  a pointer to a struct stat for this entry, an integer
       describing its type, and a pointer to a struct FTW. The  type  will  be
       one of the following: FTW_F, FTW_D, FTW_DNR, FTW_SL, FTW_NS (with mean-
       ing as above; FTW_SL occurs only with FTW_PHYS set) or

       FTW_DP Item is a directory and all its descendants  have  been  handled
              already. (This occurs only with FTW_DEPTH set.)

       FTW_SLN
              Item  is  a symbolic link pointing to a nonexisting file.  (This
              occurs only with FTW_PHYS unset.)

       The struct FTW pointed at by the fourth argument to fn() has  at  least
       the  fields  base,  the  offset  of the item's filename in the pathname
       given as first argument of fn(), and level, the depth of the item rela-
       tive to the starting point (which has depth 0).

NOTES
       The function nftw() and the use of FTW_SL with ftw() were introduced in
       XPG4v2.

       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.

CONFORMING TO
       AES, SVID2, SVID3, XPG2, XPG3, XPG4, XPG4v2.

SEE ALSO
       stat(2)




Linux                             1999-06-25                            FTW(3)