#include <ftw.h>
int ftw(const char *path, int (*fn)(const
char *,
const struct stat *ptr, int flag),
int
ndirs);
The ftw() function shall recursively descend the directory hierarchy rooted in path. For each object in the hierarchy, ftw() shall call the function pointed to by fn, passing it a pointer to a null-terminated character string containing the name of the object, a pointer to a stat structure containing information about the object, and an integer. Possible values of the integer, defined in the <ftw.h> header, are:
If the integer is FTW_DNR, descendants of that directory shall not be processed. If the integer is FTW_NS, the stat structure contains undefined values. An example of an object that would cause FTW_NS to be passed to the function pointed to by fn would be a file in a directory with read but without execute (search) permission.
The ftw() function shall visit a directory before visiting any of its descendants.
The ftw() function shall use at most one file descriptor for each level in the tree.
The argument ndirs should be in the range [1, {OPEN_MAX}].
The tree traversal shall continue until either the tree is exhausted, an invocation of fn returns a non-zero value, or some error, other than [EACCES], is detected within ftw().
The ndirs argument shall specify the maximum number of directory streams or file descriptors or both available for use by ftw() while traversing the tree. When ftw() returns it shall close any directory streams and file descriptors it uses not counting any opened by the application-supplied fn function.
The results are unspecified if the application-supplied fn function does not preserve the current working directory.
The ftw() function need not be reentrant. A function that is not required to be reentrant is not required to be thread-safe.
If the tree is exhausted, ftw() shall return 0. If the function pointed to by fn returns a non-zero value, ftw() shall stop its tree traversal and return whatever value was returned by the function pointed to by fn. If ftw() detects an error, it shall return -1 and set errno to indicate the error.
If ftw() encounters an error other than [EACCES] (see FTW_DNR and FTW_NS above), it shall return -1 and set errno to indicate the error. The external variable errno may contain any error value that is possible when a directory is opened or when one of the stat functions is executed on a directory or file.
The ftw() function shall fail if:
The ftw() function may fail if:
In addition, if the function pointed to by fn encounters system errors, errno may be set accordingly.
The following sections are informative.
The following example walks the current directory structure, calling the fn function for every directory entry, using at most 10 file descriptors:
#include <ftw.h>
...
if (ftw(".", fn, 10) != 0) {
perror("ftw"); exit(2);
}
The ftw() function may allocate dynamic storage during its operation. If ftw() is forcibly terminated, such as by longjmp() or siglongjmp() being executed by the function pointed to by fn or an interrupt routine, ftw() does not have a chance to free that storage, so it remains permanently allocated. A safe way to handle interrupts is to store the fact that an interrupt has occurred, and arrange to have the function pointed to by fn return a non-zero value at its next invocation.
longjmp(), lstat(), malloc(), nftw(), opendir(), siglongjmp(), stat(), the Base Definitions volume of IEEE Std 1003.1-2001, <ftw.h>, <sys/stat.h>