Passing code to the generated lex program

The lex command passes C code, unchanged, to the lexical analyzer in the following circumstances:

• Lines beginning with a blank or tab in the definitions section, or at the start of the rules section before the first rule, are copied into the lexical analyzer. If the entry is in the definitions section, it is copied to the external declaration area of the lex.yy.c file. If the entry is at the start of the rules section, the entry is copied to the local declaration area of the yylex subroutine in the lex.yy.c file.
• Lines that lie between delimiter lines containing only %{ (percent sign, left brace) and %} (percent sign, right brace) either in the definitions section or at the start of the rules section are copied into the lexical analyzer in the same way as lines beginning with a blank or tab.
• Any lines occurring after the second %% (percent sign, percent sign) delimiter are copied to the lexical analyzer without format restrictions.