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Linux 2.6 - man page for nftw (linux section 3posix)

NFTW(P) 			    POSIX Programmer's Manual				  NFTW(P)

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 depth, 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.

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

       FTW_F
	      The object is a file.

       FTW_D
	      The object is a directory.

       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_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.)

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

       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.

	* 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  depth  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 reentrant. A function that is not required to be reentrant
       is not required to 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  the  path  argument  exceeds {PATH_MAX} or a pathname component 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 is not a directory.

       EOVERFLOW
	      A field in the stat structure cannot be represented correctly in the  current  pro-
	      gramming 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 {OPEN_MAX} file descriptors are currently open in the calling process.

       ENAMETOOLONG
	      Pathname resolution of a symbolic link produced an intermediate result whose length
	      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 example walks the /tmp directory and its subdirectories, calling the nftw()
       function for every directory entry, to a maximum of 5 levels deep.

	      #include <ftw.h>
	      ...
	      int nftwfunc(const char *, const struct stat *, int, struct FTW *);

	      int nftwfunc(const char *filename, const struct stat *statptr,
		  int fileflags, struct FTW *pfwt)
	      {
		  return 0;
	      }
	      ...
	      char *startpath = "/tmp";
	      int depth = 5;
	      int flags = FTW_CHDIR | FTW_DEPTH | FTW_MOUNT;
	      int ret;

	      ret = nftw(startpath, nftwfunc, depth, flags);

APPLICATION USAGE
       None.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       lstat()	,  opendir()  ,  readdir()  ,  stat()  ,   the	 Base	Definitions   volume   of
       IEEE Std 1003.1-2001, <ftw.h>

COPYRIGHT
       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable	Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					  NFTW(P)


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