Why two numbers not summarized in script?

Question

I am newer in bash. I try to create script that summarizetwo numbers:

Here is script:

echo "the result is:" expr $1+$2

Here how I call the script:

./scr3 50 98

And here is result that I get after the script executed:

the result is: expr 50+98

While I get the the string with two summarized numbers I expect to get the summarize of two numbers.

My question is why I don't get the result of summarize of the two numbers?

You aren't telling it to *run* `expr` here at all. You're passing `expr` as an *argument*. Arguments passed to `echo` are strings for it to print. — Charles Duffy, Jan 08 '19 at 23:01

score 1 · Accepted Answer · answered Jan 08 '19 at 23:02

Why? Because echo prints its arguments, and you're passing expr as an argument.

A best-practice alternative would be:

echo "The result is: $(( $1 + $2 ))"

...though the a smaller change (albeit to very inefficient code; expr is an artifact of the 1970s, made irrelevant with the introduction of $(( )) in the 1992 POSIX sh standard, and should never be used in new development) is simply:

echo "The result is: $( expr "$1" + "$2" )"

Why two numbers not summarized in script?

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