Shell commands notation
Shell
echo - $$
– Displays current shell process
$?
– Prints the exit value of the command to the screen
Exit code 0
– Means command completed successfully
$!
– PID of last job run in background
$*
– Expands all parameters passed
$$
– Contains current process ID
$@
– Each passed parameter expands to a different word
$0
– Show the name of the shell or script
$_
– Set at shell startup and contains the absolute file name of the shell/script being execute; expands last argument to the previous command