Change your password - $ passwd
Display time and date - $ date
Display the current time in the following format: HH:MM:SS A/PM - $ date +%r
Use $ date --help or $ man date
to get the format options
Determine the file type - $ file FILE
Reuse the argument from the previous command - $ command <Esc> .
display the size of a file - $ wc FILE
Display the number of lines in FILE - $ wc -l FILE
Display the number of words in FILE - $ wc -w FILE
Display the number of characters in FILE - $ wc -c FILE
Display the first 10 lines of FILE - $ head FILE
Display the last 10 lines of FILE - $ tail FILE
Display the last 20 lines of FILE - $ tail -n 20 FILE