_~  : the current user's home directory (e.g. /home/user)

_$  : used to access a variable (e.g. $home)

_&  : used to put a command in the background (e.g. afni &)

•*  : wildcard, matching zero or more characters (e.g. ls AFNI_d*)

•?  : wildcard, matching exactly one character (e.g. ls AFNI_data?)

•\  : command line continuation (must be the last character on the line)

•'  : the shell will not evaluate special characters contained within these quotes

•    (e.g. echo '$HOME' gives $HOME, not /home/user)

•"  : the shell will evaluate $variables and `commands` contained within these

•    (e.g.  echo "[*] my home dir is $HOME")

•    (e.g.  echo "the numbers are 'count -digits 2 7 12'" )

•`  : execute the command contained within these quotes, and replace the quoted

•     part with the output of the contained command

•    (e.g.  echo "the numbers are `count -digits 2 7 12`" )