Multiplication on command line terminal

Question

I\'m using a serial terminal to provide input into our lab experiment. I found that using

$ echo \"5X5\"

just returns a string of \"

Answer 1

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

echo "3 * 2.19" | bc -l 
6.57

Answer 2

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.

Answer 3

The classical solution is:

 expr 5 \* 5

Another nice option is:

 echo 5 5\*p | dc

Both of these solutions will only work with integer operands.

Answer 4

Internal Methods

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

$ echo $(( 5 * 5 ))
25

External Methods

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

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

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

Answer 5

If you like python and have an option to install a package, you can use this utility that I made.

# install pythonp
python -m pip install pythonp

pythonp "5*5"
25

pythonp "1 / (1+math.exp(0.5))"
0.3775406687981454

# define a custom function and pass it to another higher-order function
pythonp "n=10;functools.reduce(lambda x,y:x*y, range(1,n+1))"     
3628800

Answer 6

I have a simple script I use for this:

me@mycomputer:~$ cat /usr/local/bin/c

#!/bin/sh

echo "$*" | sed 's/x/\*/g' | bc -l

It changes x to * since * is a special character in the shell. Use it as follows:

• c 5x5
• c 5-4.2 + 1
• c '(5 + 5) * 30' (you still have to use quotes if the expression contains any parentheses).