Variables

All variables are treated as strings.

Important: when declaring a variable, no space should be used around =.

Using the $ symbol, the value of a variable, command, or calculation is expanded.

#!/bin/bash
 
x=1
y=2
w=this
s="is a string"
 
a=$((x + y))  # expand each var and expand the arithmetic calc
echo $a
 
b="$w $s"  # expand each var and concatenate them
echo $b
 
c=$(date '+%A %d  %B, %H:%M')  # expand the result of a command
echo $c

Info: for command evaluations use single brackets (..), while for arithmetic evaluations use double brackets ((..)). In the latter case the $ symbol before the variable names can be omitted.