Sending arguments to ftw()

Question

Is there a way to send arguments to ftw() to be used in process each file/directory on the path? It's a bit difficult to have the argument concerned as a global variable due to multithreading issues, i.e having the value as global will be visible to all threads and that would be wrong.

Answer 1

A properly designed C callback interface has a void* argument that you can use to pass arbitrary data from the surrounding code into the callback. [n]ftw does not have such an argument, so you're kinda up a creek.

If your compiler supports thread-local variables (the __thread storage specifier) you can use them instead of globals; this will work but is not really that much tidier than globals.

If your C library has the fts family of functions, use those instead. They are available on most modern Unixes (including Linux, OSX, and recent *BSD) and gnulib has a fallback implementation.