Naming Rules (The GNU Awk User’s Guide)

A number of rules apply to the namespace and component names, as follows.

It is a syntax error to use qualified names for function parameter names.
It is a syntax error to use any standard awk reserved word (such as if or for), or the name of any standard built-in function (such as sin() or gsub()) as either part of a qualified name. Thus, the following produces a syntax error:

@namespace "example" function gsub(str, pat, result) { … }
Outside the awk namespace, the names of the additional gawk built-in functions (such as gensub() or strftime()) may be used as component names. The same set of names may be used as namespace names, although this has the potential to be confusing.
The additional gawk built-in functions may still be called from outside the awk namespace by qualifying them. For example, awk::systime(). Here is a somewhat silly example demonstrating this rule and the previous one:

BEGIN { print "in awk namespace, systime() =", systime() } @namespace "testing" function systime() { print "in testing namespace, systime() =", awk::systime() } BEGIN { systime() }

When run, it produces output like this:

$ gawk -f systime.awk -| in awk namespace, systime() = 1500488503 -| in testing namespace, systime() = 1500488503
gawk pre-defined variable names may be used: NF::NR is valid, if possibly not all that useful.