7.4 Things to Try

• Macro names that begin with uppercase letters are for your use. Names that begin with lowercase letters are reserved for sendmail 's use. Twenty-seven special characters are also reserved by sendmail for use as operators. What happens if you try to define a macro whose name is another character, such as a tab or an underscore?

• What happens if you try to define a macro whose name is an operator?

• Using the -d35.9 command-line switch, determine what happens if you define two macros, each with the same name.

• Any sendmail.cf command may be continued and extended by beginning the next line with a tab or a space. Using the -d35.9 command-line switch, determine the effect of continuing a macro definition. For example,

  D{FOO}something
  
  tab
     somethingmore

• The text value of a macro must immediately follow the name of that macro, with no intervening space. Can the text value contain arbitrary spaces or tabs?

• Using grep (1), find all the D commands in your site's actual sendmail.cf file. If you find any that begin with a lowercase letter and that you haven't seen before, try looking them up in Chapter 31, Defined Macros .