The awk language has evolved over the years. Full details are
provided in The Evolution of the awk Language.
The language described in this Web page
is often referred to as “new awk.”
By analogy, the original version of awk is
referred to as “old awk.”
On most current systems, when you run the awk utility
you get some version of new awk.4 If your system’s standard
awk is the old one, you will see something like this
if you try the following test program:
$ awk 1 /dev/null error→ awk: syntax error near line 1 error→ awk: bailing out near line 1
In this case, you should find a version of new awk,
or just install gawk!
Throughout this Web page, whenever we refer to a language feature
that should be available in any complete implementation of POSIX awk,
we simply use the term awk. When referring to a feature that is
specific to the GNU implementation, we use the term gawk.
Only
Solaris systems still use an old awk for the
default awk utility. A more modern awk lives in
/usr/xpg6/bin on these systems.