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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
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 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
original Standard can be obtained online at http://www.opengroup.org/unix/online.html .