cat concatenate (combine) two or more files
cd change to another directory
chmod change mode (security permissions) of file or directory
ugo+-rwx user (owner), group, other (world), add, remove, read, write, execute
cp copy file
 -r copy directory tree
df show disk free information
find find files in a directory tree
finger display user information
grep list text lines containing particular characters
groups show your security group memberships
kill kill process
-9 kill process immediately
lpr send to printer
-P send to another printer
lpq show status of print queue
-P show print jobs in a different print queue
lprm remove print job from printer
-P remove from a different print queue
ls list contents of current directory
-l long (detailed) listing
man display portion of online Unix manual
 -k display command descriptions relating to subject keyword
mkdir make new directory
more display contents of file
mv move or rename file or directory
ps aux list status of all processes (running programs)
pwd print working (current) directory
rm remove file
-r remove directory tree
rmdir remove an empty directory
.. parent directory
. current directory
* wildcard representing any combination of characters
? wildcard representing exactly one character
~ your home directory
~userid userid’s home directory
> send output to file
>> append (add) output to file
| pipe output from one command as input to another