FTW(3) BSD Programmer's Manual FTW(3)
ftw, nftw - traverse (walk) a file tree
#include <ftw.h>
int
ftw(const char *path, int (*fn)(const char *, const struct stat *, int),
int maxfds);
int
nftw(const char *path,
int (*fn)(const char *, const struct stat *, int, struct FTW *),
int maxfds, int flags);
These functions are provided for compatibility with legacy code. New code
should use the fts(3) functions.
The ftw() and nftw() functions traverse (walk) the directory hierarchy
rooted in path. For each object in the hierarchy, these functions call
the function pointed to by fn. The ftw() function passes this function a
pointer to a NUL-terminated string containing the name of the object, a
pointer to a stat structure corresponding to the object, and an integer
flag. The nftw() function passes the aforementioned arguments plus a
pointer to a FTW structure as defined by <ftw.h> (shown below):
struct FTW {
int base; /* offset of basename into pathname */
int level; /* directory depth relative to starting point */
};
Possible values for the flag passed to fn are:
FTW_F A regular file.
FTW_D A directory being visited in pre-order.
FTW_DNR A directory which cannot be read. The directory will not be des-
cended into.
FTW_DP A directory being visited in post-order (nftw() only).
FTW_NS A file for which no stat(2) information was available. The con-
tents of the stat structure are undefined.
FTW_SL A symbolic link.
FTW_SLN A symbolic link with a non-existent target (nftw() only).
The ftw() function traverses the tree in pre-order. That is, it processes
the directory before the directory's contents.
The maxfds argument specifies the maximum number of file descriptors to
keep open while traversing the tree. It has no effect in this implementa-
tion.
The nftw() function has an additional flags argument with the following
possible values:
FTW_PHYS Physical walk: don't follow symbolic links.
FTW_MOUNT The walk will not cross a mount point.
FTW_DEPTH Process directories in post-order. Contents of a directory are
visited before the directory itself. By default, nftw()
traverses the tree in pre-order.
FTW_CHDIR Change to a directory before reading it. By default, nftw()
will change its starting directory. The current working direc-
tory will be restored to its original value before nftw() re-
turns.
If the tree was traversed successfully, the ftw() and nftw() functions
return 0. If the function pointed to by fn returns a non-zero value,
ftw() and nftw() will stop processing the tree and return the value from
fn. Both functions return -1 if an error is detected.
The ftw() and nftw() functions may fail and set errno for any of the er-
rors specified for the library functions close(2), open(2), stat(2),
malloc(3), opendir(3) and readdir(3). If the FTW_CHDIR flag is set, the
nftw() function may fail and set errno for any of the errors specified
for chdir(2). In addition, either function may fail and set errno as fol-
lows:
[EINVAL] The maxfds argument is less than 1 or greater than
OPEN_MAX.
chdir(2), close(2), open(2), stat(2), fts(3), malloc(3), opendir(3),
readdir(3)
The ftw() and nftw() functions conform to IEEE Std 1003.1-2001
("POSIX.1").
The maxfds argument is currently ignored.
MirBSD #10-current May 20, 2003 1