6. Walk + File
Write a program middle.c:
./middle directory
Walks over all files in the directory (not recursive)
Prints out middle line from any file (skipping other filesystem objects — directories, devices etc)
All files are treated as text ones (e. g. /usr/share/bash4/ directory)
Middle line is the line that overlaps ½ of the file length or starts just ant the ½ of the file