Example
expr or Evaluate expressions evaluates an expression and writes the result on standard output
Basic arithmetics
expr 2 + 3
5
When multiplying, you need to escape the * sign
expr 2 \* 3
6
You can also use variables
a=2
expr $a + 3
5
Keep in mind that it only supports integers, so expression like this
expr 3.0 / 2
will throw an error expr: not a decimal number: '3.0'.
It supports regular expression to match patterns
expr 'Hello World' : 'Hell\(.*\)rld'
o Wo
Or find the index of the first char in the search string
This will throw
expr: syntax erroron Mac OS X, because it uses BSD expr which does not have the index command, while expr on Linux is generally GNU expr
expr index hello l
3
expr index 'hello' 'lo'
3
