ftw(3C)                 LIBRARY FUNCTIONS                 ftw(3C)



NAME
     ftw, nftw - walk a file tree

SYNOPSIS
     #include <ftw.h>

     int ftw (const char *path, int (*fn) (const  char  *,  const
     struct stat *, int), int depth);

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

DESCRIPTION
     ftw recursively descends the directory hierarchy  rooted  in
     path.   For  each  object  in  the  hierarchy, ftw calls the
     user-defined function fn, passing it a pointer  to  a  null-
     terminated  character  string  containing  the  name  of the
     object, a pointer to a stat structure (see stat(2)) contain-
     ing  information about the object, and an integer.  Possible
     values of the integer, defined in the <ftw.h>  header  file,
     are:

     FTWF       The object is a file.

     FTWD       The object is a directory.

     FTWDNR     The object is a directory that cannot  be  read.
                 Descendants  of  the  directory will not be pro-
                 cessed.

     FTWNS      stat failed on the object  because  of  lack  of
                 appropriate  permission  or the object is a sym-
                 bolic link that points to a  non-existent  file.
                 The stat buffer passed to fn is undefined.

     ftw visits a directory before visiting any  of  its  descen-
     dants.

     The tree traversal continues until the tree is exhausted, an
     invocation  of  fn returns a nonzero value, or some error is
     detected within ftw (such as an I/O error).  If the tree  is
     exhausted, ftw returns zero.  If fn returns a nonzero value,
     ftw stops its tree traversal and returns whatever value  was
     returned  by fn.  If ftw detects an error other than EACCES,
     it returns -1, and sets the error type in errno.  The  func-
     tion  nftw  is  similar to ftw except that it takes an addi-
     tional argument, flags.  The flags field is used to specify:

     FTWPHYS    Physical walk, does not follow  symbolic  links.
                 Otherwise,  nftw  will follow links but will not
                 walk down any path that crosses itself.




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ftw(3C)                 LIBRARY FUNCTIONS                 ftw(3C)



     FTWMOUNT   The walk will not cross a mount point.

     FTWDEPTH   All subdirectories will be  visited  before  the
                 directory itself.

     FTWCHDIR   The walk will change to  each  directory  before
                 reading it.

     The function nftw calls fn with four arguments at each  file
     and  directory.   The  first argument is the pathname of the
     object, the second is a pointer  to  the  stat  buffer,  the
     third  is  an integer giving additional information, and the
     fourth is a struct FTW which contains the following members:
          int base;
          int level;
     base is the offset into the pathname of the base name of the
     object.   level  indicates the depth relative to the rest of
     the walk, where the root level is zero.  The values  of  the
     third argument are as follows:

     FTWF       The object is a file.

     FTWD       The object is a directory.

     FTWDP      The object is  a  directory  and  subdirectories
                 have been visited.

     FTWSLN     The object is a symbolic link that points  to  a
                 non-existent file.

     FTWDNR     The object is a directory that cannot  be  read.
                 fn  will  not  be  called for any of its descen-
                 dants.

     FTWNS      stat failed on the object  because  of  lack  of
                 appropriate  permission.  The stat buffer passed
                 to fn is undefined.   stat  failure  other  than
                 lack of appropriate permission (EACCESS) is con-
                 sidered an error and nftw will return -1.

     Both ftw and nftw use one file descriptor for each level  in
     the  tree.   The  depth  argument  limits the number of file
     descriptors so used.  If depth  is  zero  or  negative,  the
     effect  is  the  same  as  if  it were 1.  depth must not be
     greater than the number of file descriptors currently avail-
     able  for  use.   ftw  will  run more quickly if depth is at
     least as large as the number of levels in  the  tree.   When
     ftw  and  nftw  return they close any file descriptors which
     they have opened, they do not  close  any  file  descriptors
     which may have been opened by fn.





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ftw(3C)                 LIBRARY FUNCTIONS                 ftw(3C)



SEE ALSO
     stat(2), malloc(3C).

NOTES
     Because ftw is recursive, it is possible for it to terminate
     with  a  memory  fault when applied to very deep file struc-
     tures.

     ftw uses malloc(3C) to allocate dynamic storage  during  its
     operation.   If  ftw  is  forcibly  terminated,  such  as by
     longjmp being executed by fn or an  interrupt  routine,  ftw
     will  not  have  a  chance  to free that storage, so it will
     remain permanently allocated.  A safe way to  handle  inter-
     rupts  is  to store the fact that an interrupt has occurred,
     and arrange to have fn return a nonzero value  at  its  next
     invocation.







































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