GAWK: Effective AWK Programming

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298 GAWK: Effective AWK ProgrammingThis section briefly lists extensions and possible improvements that indicate the directionswe are currently considering for gawk. The file ‘FUTURES’ in the gawk distribution liststhese extensions as well.Following is a list of probable future changes visible at the awk language level:Loadable module interfaceIt is not clear that the awk-level interface to the modules facility is as good as itshould be. The interface needs to be redesigned, particularly taking namespaceissues into account, as well as possibly including issues such as library searchpath order and versioning.RECLEN variable for fixed-length recordsAlong with FIELDWIDTHS, this would speed up the processing of fixed-lengthrecords. PROCINFO["RS"] would be "RS" or "RECLEN", depending upon whichkind of record processing is in effect.Additional printf specifiersThe 1999 ISO C standard added a number of additional printf format specifiers.These should be evaluated for possible inclusion in gawk.DatabasesIt may be possible to map a GDBM/NDBM/SDBM file into an awk array.More lint warningsThere are more things that could be checked for portability.Following is a list of probable improvements that will make gawk’s source code easier towork with:Loadable module mechanicsThe current extension mechanism works (see Section C.3 [Adding New BuiltinFunctions to gawk], page 287), but is rather primitive. It requires a fairamount of manual work to create and integrate a loadable module. Nor is thecurrent mechanism as portable as might be desired. The GNU libtool packageprovides a number of features that would make using loadable modules mucheasier. gawk should be changed to use libtool.Loadable module internalsThe API to its internals that gawk “exports” should be revised. Too manythings are needlessly exposed. A new API should be designed and implementedto make module writing easier.Better array subscript managementgawk’s management of array subscript storage could use revamping, so thatusing the same value to index multiple arrays only stores one copy of the indexvalue.Integrating the DBUG libraryIntegrating Fred Fish’s DBUG library would be helpful during development,but it’s a lot of work to do.Following is a list of probable improvements that will make gawk perform better:
Appendix C: Implementation Notes 299Compilation of awk programsgawk uses a Bison (YACC-like) parser to convert the script given it into asyntax tree; the syntax tree is then executed by a simple recursive evaluator.This method incurs a lot of overhead, since the recursive evaluator performsmany procedure calls to do even the simplest things.It should be possible for gawk to convert the script’s parse tree into a C programwhich the user would then compile, using the normal C compiler and a specialgawk library to provide all the needed functions (regexps, fields, associativearrays, type coercion, and so on).An easier possibility might be for an intermediate phase of gawk to convert theparse tree into a linear byte code form like the one used in GNU Emacs Lisp.The recursive evaluator would then be replaced by a straight line byte codeinterpreter that would be intermediate in speed between running a compiledprogram and doing what gawk does now.Finally, the programs in the test suite could use documenting in this book.See Section C.2 [Making Additions to gawk], page 284, if you are interested in tacklingany of these projects.
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GAWK: Effective AWK Programming

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