Awk from introduction to earth (16) discussion on the types of awk variables -- about the two types of numbers and strings

awk（ Variable 、 Array elements and fields ） The scalar object in is Dynamic type Of . This means that their types can change as the program runs , From no type before use , To string or number , Then from string to number or from number to string , As the program goes .

You can't do many things with untyped variables , Except to tell them that they are untyped . The following procedure is for a To test ; When a When never assigned , Test success . It also uses built-in typeof() Function to display a The type of ：

$ gawk 'BEGIN { print (a == "" && a == 0 ?
> "a is untyped" : "a has a type!") ; print typeof(a) }'
a is untyped
unassigned

Similarly , When assigning a string value to a scalar , Scalars have string types , For example, from a string constant or from another scalar with a string type ：

gawk 'BEGIN { a = 42 ; print typeof(a) ;b = a ; print typeof(b) }'

up to now , All this is simple and clear . however , When awk What happens when processing data from users ？ Let's start with the field data . What should the following command produce as output ？

echo hello | awk '{ printf("%s %s < 42\n", $1,
                           ($1 < 42 ? "is" : "is not")) }'

because ’hello’ Is alphabetic data ,awk Only string comparison . In the internal ࿰