gauss 21> mysum
1
2
8
10
^D
    21.00000000000000    

gauss 22> mysum < first100
    5050.000000000000    

gauss 23> mysum
12
2
8
a
10
b
^D
    21.00000000000000    
            2 invalid inputs

gauss 24> mysum < first100 > mysum_result
gauss 25> more !$
more mysum_result
    5050.000000000000