/usr/bin/chmod 751 data/subdir
/usr/bin/chmod 640 data/empty.txt
/usr/bin/chmod 640 data/FIRST.txt
/usr/bin/chmod 400 data/.hidden.txt
/usr/bin/chmod 640 data/pwd.txt
/usr/bin/chmod 640 data/yat.txt
./bin/ls -a data
./bin/ls -s data
./bin/ls -sa data
./bin/ls -ap data
./bin/head -n 1 Makefile
quit