cp  Copy files  
mv       Move or rename files/directories  
rm       Remove files or directories  
ls     List the contents of a directory  
cd        Change working directory  
pwd    Display the pathname of the current working directory  
mkdir  Make a directory  
rmdir   Remove directories, if it is empty
umask Show the permissions that are given to view files by default  
 
grep   Search a file for a string or regular expression  
cat      Concatenate and display  
 
groupadd Create a user group  
chgrp            Change the group ownership of a file  
chmod          Change the permissions mode of a file  
chown  Change owner  
 
set        Set the values of all shell variables  
setenv  Set environment variables  
env       Obtain or alter environment variables for command execution  
 
echo   Echo arguments to the standard options  
more   Browse or page through a text file or an output of a command
script   Save the output of a command or process
 
find   Find files by name, or by other characteristics  
 
man   Display reference manual pages; find reference pages by keyword  
 
passwd  Change user password
kill        Terminate a process  
ps         Display the status of current processes  
top        Display all system processes
rlogin   Start a login to a different machine  
uname   Display name of the current system
uptime  Get the system up time