nftw(), nftw64()

Walk a file tree


#include <ftw.h>

int nftw( const char *path, 
         int (*fn)( const char *fname,
                    const struct stat *sbuf,
                    int flags, 
                    struct FTW *ftw),
         int depth,
         int flags);

int nftw64( const char *path, 
            int (*fn)( const char *fname,
                       const struct stat64 *sbuf,
                       int flags, 
                       struct FTW *ftw),
            int depth,
            int flags);


The path of the directory whose file tree you want to walk.
A pointer to a function that you want to call for each file; see below.
The maximum number of file descriptors that nftw() can use. The nftw() function uses one file descriptor for each level in the tree.

If depth is zero or negative, the effect is the same as if it were 1. The depth must not be greater than the number of file descriptors currently available for use. The nftw() function is faster if depth is at least as large as the number of levels in the tree.

The value of flags is constructed by the bitwise ORing of values from the following list, defined in the <ftw.h> header file.
If set, nftw() changes the current working directory to each directory as it reports files in that directory.
If set, nftw() reports all files in a directory before reporting the directory itself (otherwise the directory is reported before any file it contains).
If set, nftw() only reports files on the same filesystem as path.
If set, nftw() performs a physical walk and doesn't follow any symbolic link.



Use the -l c option to qcc to link against this library. This library is usually included automatically.

Note: These functions are in libc.a, but not in (in order to save space).


The nftw() and nftw64() functions recursively descend the directory hierarchy identified by path. The nftw64() function is a large-file support version of nftw().

Note: In QNX Neutrino 6.6 or later, the large-file support functions and data types appear in the name space only if you define _LARGEFILE64_SOURCE when you compile your code. For more information, see "Classification" in What's in a Function Description?

For each object in the hierarchy, nftw() calls the user-defined function fn(), passing to it:

The tree traversal continues until the tree is exhausted, an invocation of fn() returns a nonzero value, or some error is detected within nftw() (such as an I/O error). If the tree is exhausted, nftw() returns zero. If fn() returns a nonzero value, nftw() stops its tree traversal and returns whatever value was returned by fn().

When nftw() returns, it closes any file descriptors it opened; it doesn't close any file descriptors that may have been opened by fn().


An error (other than EACCES) occurred (errno is set).


nftw() is POSIX 1003.1; nftw64() is Large-file support

Cancellation point Yes
Interrupt handler No
Signal handler Yes
Thread Yes


Because nftw() is recursive, it might terminate with a memory fault when applied to very deep file structures.

This function uses malloc() to allocate dynamic storage during its operation. If nftw() is forcibly terminated, for example if longjmp() is executed by fn() or an interrupt routine, nftw() doesn't 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 fn() return a nonzero value at its next invocation.