Multiplication on command line terminal

Bash supports arithmetic expansion with $(( expression )). For example:

$ echo $(( 5 * 5 ))
25

A number of utilities provide arithmetic, including bc and expr.

$ echo '5 * 5' | /usr/bin/bc
25

$ /usr/bin/expr 5 \* 5
25

Yes, you can use bash's built-in Arithmetic Expansion $(( )) to do some simple maths

$ echo "$((5 * 5))"
25

Check the Shell Arithmetic section in the Bash Reference Manual for a complete list of operators.

For sake of completeness, as other pointed out, if you need arbitrary precision, bc or dc would be better.

For more advanced and precise math consider using bc(1).

echo "3 * 2.19" | bc -l 
6.57

The classical solution is:

 expr 5 \* 5

expr will only work with integer operands. Another nice option is:

 echo 5 5\*p | dc

dc can be made to work with non-integer operands.

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