2. Configuration

Basically, there are four ways to change slrn's behaviour:

• environment variables
• a global configuration file
• a personal configuration file
• command line options

The list is sorted by priority - environment variables are overridden by settings in configuration files that are in turn overridden by command line options.

Have a look at the following chapters for a detailed description of the above configuration facilities.

Note: Please do not use options that are called ``obsolete'' in this manual. They are only included for backwards compatibility and will probably be removed before version 1.0 is released.

2.1 A brief introduction to the built-in S-Lang prompt

When trying various configuration settings, you may find it quite inconvenient to constantly toggle between slrn and your editor and to restart slrn each time you made a change. Maybe you also want to play around with some settings without making (permanent) changes to your config file. In these cases, making yourself familiar with the built-in S-Lang prompt of slrn can be worthwhile.

You get to the prompt by calling evaluate_cmd (by default bound to ``CTRL-X ESC'') in either group or article mode. You will notice that the bottom status line changes and displays S-Lang> - behind that prompt, you can enter your commands. Basically, you can do anything here that you could do in a macro, so if you want to explore the full capabilities of this prompt, you'll have to read the documentation that comes with S-Lang and look at the file slrnfuns.txt that comes with slrn.

However, you can also do some simple things without understanding much about S-Lang:

• To find out the current value of a config variable, use a command like this one:

          message(string(get_variable_value("use_metamail")))
  

  After this, the current value of the variable will appear in the bottom status line. By the way, the call to string() is only needed when querying an integer variable, so you can omit it if you want when getting the value of a string variable.
• If you want to set a config variable at runtime, you need to know whether its type is integer or string (if in doubt, look it up in this manual). To set a variable, use something like

          set_integer_variable("use_metamail", 0)
            % for integer variables
          set_string_variable("metamail_command", "metamutt")
            % for string variables
  

  Note that changing a variable does not always have an immediate effect: For example, changing sorting_method does not automatically imply a re-sorting of the articles. By the way, you can call the intrinsic function sort_by_sorting_method from the S-Lang prompt afterwards in this specific case.
• You can also load macros dynamically using a line like

          () = evalfile("my-macro.sl")
  

  Note that you need those funny leading brackets and the equals sign in this case, because evalfile returns 1 on success. Using the given notation, we simply ignore the returned value. If we didn't do anything with it, it would be left on the stack and when this happens too often, you'll get a stack overflow at some point. If you really want to understand this, please read the file slang.txt that comes with the S-Lang documentation. Otherwise, simply use the notation given here.