NFTW(P) POSIX Programmer's Manual NFTW(P)NAMEnftw - 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 fol‐
low 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 func‐
tion 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 unde‐
fined. 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 rel‐
ative 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 programming 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 ALSOlstat() , 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 original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 NFTW(P)
