C Shell Quoting

It is important to know the meaning of different quotation characters in c shell.

• single quotes: ' $-$$>$ turn off special meaning of all characters until the next single quote is found.
  Example:
  echo $PATH
  echo '$PATH'
  echo Hey, what's next? Mike's #1 friend has $value.
  (output: Hey, whats next? Mikes )
  Everything after # is ignored, since # starts comment in shell
  

• double quotes: '' $-$$>$ work almost like single quotes, but double quoting allows the char
  $ (dollar sign),
  `(back-quote),
  $\backslash$ (backslash)
  to keep their special meaning.
  Example:
  

  echo "Hey, what's next? Mike's #1 friend has $value."
  

• pair of back-quotes: ` does command substitution
  Example: How to send an e-mail message to all the users logged on to the system.
  First use the command
  who $\vert$ cut -c1-8
  which will list all users currently log in.
  who $\vert$ cut -c1-8 $\vert$ sort -u
  will sort them in alphabetical order and will only display unique names
  mail ` who $\vert$ cut -c1-8 $\vert$ sort -u`
  will send e-mail to all of them.
  If you are not sure, how this command works (or you really do not want to send an e-mail to everybody) replace mail command with echo command:
  

  echo ` who $\vert$ cut -c1-8 $\vert$ sort -u`.