gawk: Truth Values
6.3.1 True and False in 'awk'
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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 uppercase equivalents.
However, 'awk' is different. It borrows a very simple concept of true
and false from C. In 'awk', any nonzero numeric value _or_ any nonempty
string value is true. Any other value (zero or the null string, '""')
is false. The following program prints '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 "nonzero or non-null" rule:
the string constant '"0"' is actually true, because it is non-null.
(d.c.)
Info Catalog
gawk: Truth Values and Conditions
gawk: Typing and Comparison