Dollar sign

Expand a Bash variable. More information: https://gnu.org/software/bash/manual/bash.html#Shell-Variables.

• Print a variable:

echo $VARIABLE

• Print the exit status of the previous command:

echo $?

• Print a random number between 0 and 32767:

echo $RANDOM

• Print one of the prompt strings:

echo $PS1|PS2|PS3|PS4

• Expand with the output of command and run it. Same as enclosing command in backtics:

$(command)