A viewpath mounts one directory tree on top of another. Viewpath mounts directories can be chained. All levels but the top in a chain are readonly. The stream supports file descriptor exchange. Set the debug trace level to level .
Higher levels produce more output.
If bottom is a directory then the directory top is viewpathed on top of bottom . The default value is ksh . If id is greater than 1 then intercepted system calls for the current process and all children will be traced. Unsupported fs paths are silently ignored. 3d ignores calls not present in a particular host system.