Question

I am trying to build a scanner for AWK source code using (F)Lex analysis. I have been able to identify AWK keyworkds, comments, string literals, and digits however I am stuck on how to generate regular expressions for matching variable instance names since these are quite dynamic.

Could someone please help me develop a regular expression for matching AWK variables.
http://pubs.opengroup.org/onlinepubs/009695399/utilities/awk.html provides definition for the AWK language.

Variables must start with a letter but can be alphanumerical without regard to case. The only special character that can be used is an underscore (“_”). I apologize I am not very experienced with REGEX let alone regular expressions for FLEX.

Thank you for your help.

Answer 1

[a-zA-Z_][a-zA-Z_0-9]*

Alphabetic or underscore to start, followed by zero or more alphanumerics or underscore.

Special cases will be fields, which are prefixed by $:

$0
$1

and also

$NF
$i

You’ll have to decide how you’re going to deal with those.