True and False in awk

Many programming languages have a special representation for the concepts of "true" and "false." Such languages usually use the special constants true and false, or perhaps their upper-case equivalents.

awk is different. It borrows a very simple concept of true and false from C. In awk, any non-zero numeric value, or any non-empty string value is true. Any other value (zero or the null string, "") is false. The following program will print `A strange truth value' three times:

BEGIN {
   if (3.1415927)
       print "A strange truth value"
   if ("Four Score And Seven Years Ago")
       print "A strange truth value"
   if (j = 57)
       print "A strange truth value"
}

There is a surprising consequence of the "non-zero or non-null" rule: The string constant "0" is actually true, since it is non-null (d.c.).

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