I want to use the tolower() function with SunOS nawk, but all I get is

        nawk: calling undefined function tolower

The SunOS nawk is from a time before awk acquired the tolower() and toupper() functions. Either use one of the freely available awks, or or use /usr/xpg4/bin/awk (if you have it), or write your own function to do it using index, substr, and gsub.

An example of such a function is in O'Reilly's _Sed & Awk_.

Patrick TJ McPhee writes:

> SunOS includes three versions of awk. /usr/bin/awk is the old
> (pre-1989) version. /usr/bin/nawk is the new awk which appeared
> in 1989, and /usr/xpg4/bin/awk is supposed to conform to the single
> unix specification. No one knows why Sun continues to ship old awk.