Shell Commands
==============

cd
    Change Directory
pwd
    Print Working Directory
ls
    List Directory
tail -100, head -150 to extract the last 100 or first 150 rows of a file
    .
tail -n
    Return the last n, lines from a specified file
head -n
    Return the first n lines from a file
cp
    Copy
mv
    Movew
mkdir
    Make Directory
rmdir
    Remove Directory
sort, uniq respectively sort a file and remove dupicate entries (you can sort alphabetically or numerically depending on the option; default is alphabetical order)
    Sort
gzip
    compress/uncompress files
wc
    Count number of rows and words in a text file
grep
    identify all rows containing a specific string in a text file (it helps to be familiar with regular expression)
cat
    display content of text file on your screen
chmod
    change file protections, see section 2
history
    List the last commands run
cron, crontab
    Scheduling commands