There are two ways we can have the shell evaluate an expression. Either using
$((expression)) syntax or the
The former does not require proper spacing, while the latter does.
$ echo $((2+3)) 5 $ expr 2 + 3 5
Arithmetic expasion only supports integer values and no decimals.
$ expr 2.3 + 2 expr: not a decimal number: '2.3'
Here are a list of arithmetic operators.
It's important to avoid using the
= symbol when comparing numerals. The
= looks for string equality, not numeric equality. Thus, when working with arithmetic equations, be sure to use
$ [ 1 = 1 ]; echo $? 0 $ [ 092 = 92 ]; echo $? 1 $ [ 092 -eq 92 ]; echo $? 0
Here is a list of more comparison tests we can use to compare two numbers. Be sure to not use canonical notations such as
$ [ 92 > 32 ]; echo $? 0 # Looks good...(but wrong) $ [ 92 < 32 ]; echo $? 0 # Wrong $ [ 92 -gt 32 ]; echo $? 0 # There we go!
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