Jonathan Lees' List of the top 40 Unix commands

ls  = list directory
pwd =  print working directory
cd  =  change directory
cat =  concatenate files  (print files to screen)
more =  list out the files page by page
head =  list out the top of a file (default is 10 lines)
tail = display the last part of a file (default is 10 lines)
vi  =   virtual editor  (full screen editor)
      (difficult to learn but very powerful.  works on
       any unix terminal, both graphics and non-graphics)
standard input/standard output   <  vs >
pipe symbol  |   for chaining commands together
magic characters    * / & $ # ! .
regular expressions = standard searching expressions using magic/regular characters
rlogin = remote login to another machine
su  = substitute user
passwd  = change password
alias =  alias a command to some other name

du  = disk usage
f77  = fortran compiler
cc = c compiler
make = program that compiles and links programs conveniently
       uses a file called a makefile
man  =  show a manual page for a command
grep = global regular expression printer (searches files for strings...)
history = display last n commands
!!  = execute last command
!n  = execute last nth command
mv  = move (rename) a file
cp  = copy a file
rm  =  remove a file (watch out!)  use rm -i
chmod  = change mode of a file (readble writable executable)
chown  = change ownership of a file
echo   = echo back whatever
lpr = send a file to the printer
lpq =  query the printer queue
lprm = remove a plot from the printer queue
mkdir = make (create) a directory
mail = try (/ucb/mail)  mail system
nice =  run a job in low priority
source = execute a macro shell
sh = start a new shell
tar = tape archive (use "ar" for file archive)
who = find out who is on system
wc  = word count - gives number of lines words and chars in a file