Shell Programming and Scripting

Don, they would all work with nawk. Or can you show me one that does not, or give me a pointer?

That is because those scripts do not adhere to the POSIX standards for sed and awk. If they were written to be compliant, they would most likely also have worked on Solaris using /usr/xpg4/bin/awk and /usr/xpg4/bin/sed

For example in standard awk the variable RS can only be a single character. Only GNU awk and mawk support the use of a regular expression in RS as an extension to the standard.

Hi MadeInGermany,
The original awk didn't have as many built-in variables as nawk. For example, if an original awk script used a variable named RS (which was not defined by the original awk but is the record separator in nawk and in the standards) the old script could behave very differently if that variable was set to anything other than a <newline> character.

I no longer have access to the old awk scripts that failed when run with nawk or /usr/xpg4/bin/awk and don't remember which variables they used, but it was things like this that caused awk to remain compatible with the original awk rather than making it a link to nawk on Solaris systems at least through Solaris 10.