Working with the Unix OS

Development Tools
TAR
tar cf files.tar dirname # create tar of files
tar tvf files.tar
# full view of files in tar
compress files.tar # compress (tree archive)
uuencode files.tar.Z files.tar.Z > files.tar.Z.uu
elm -s "files.tar.Z.uu" neville < files.tar.Z.uu
uudecode files.tar.Z.uu | uncompress | tar xvf –
#extract files
Other compression tools such as "freeze“, "zoo", "zip", "jpeg" are freely available for UNIX systems.
Program Development
yacc a parser generator – generates a parser from a grammatical description of a language
make controlling the processes by which a complicated program is compiled
lex making lexical analysers
Example: A simple calculator
4*3*2
24
355/113
3.1415929
(1+2)*(3+4)
Grammar:
21 list: expr \n
list expr \n
expr: NUMBER
expr '+' expr
expr '-' expr
expr ’*' expr
expr '/' expr
'(' expr ') '
YACC
Yet Another Compiler-Compiler. Yacc is a powerful tool. It takes some effort to learn. Yacc-generated parsers are
small, efficient and correct.
- write the grammar
- each rule of grammar can have an action written in C – this defines the semantics
- a lexical analyser (LEX) to break input into meaningful chunks (token) for the parser
- a controlling routine to call the parser that yacc built
- Input to yacc:
%{
C statements like #include, declarations
%}
yacc declarations: lexical tokens, grammar variables, precedence and
associativity information
%%
grammar rules and actions
%%
more C statements
main() { ...; yyparse(); …}
yylex() { … }
/*
$ yacc hocl.y
$ cc y.tab.c -o hocl
61