Advanced Console Scripting

This guide will explain the more advanced concepts of the console in DarkPlaces.

Aliases are fundamental in script creation. They are the key to simplification, and often the principal part of a script.

Aliases are “shortcuts” to commands. For example, if I am too lazy to type “chmap silvercity” every time I want to play on silvercity locally, all I have to do is set up an alias that way:

alias sc "chmap silvercity"

The quotes are not needed, but it is always better to use them, as multi-command aliases need them:

alias hi say hello; say how are you?
alias hi "say hello; say how are you?"

The first alias is a shortcut to “say hello”. When the alias is saved, you will say “how are you?”.
The second alias assigns “hi” to both commands. They are executed one after the other when I enter the new “hi” command.

There are a few special variables accessible only from inside an alias. There are 80 of them, that should be enough for anything.
See Variable expansion below for more details on the use of these.

First of all, what does “variable” mean? It is any cvar ¹⁾ plus the alias parameters.
Variable expansion lets you use content from variables in other commands. Here is an example session:

]set foo "Hello World!"
]echo $foo
Hello World!

As you can see, you just need a $ in front of the variable's name to get expansion. If you want to escape $²⁾, just use $$ (not \$).

]echo I'm going to show you how to expand a cvar.
I'm going to show you how to expand a cvar.
]echo Just type this to expand timelimit: $timelimit
Just type this to expand timelimit: 20
]echo Woops, I meant $$timelimit of course!
Woops, I meant $timelimit of course!

Sometimes you may want to use the longer syntax: ${variable} if your variable name contains spaces (this won't happen often) or if you need to do “double expansion”, that is interpret the content of a variable as another variable's name, and expand this again. Example:

]set levelOne "levelTwo"
]set levelTwo $message
]echo $levelOne
levelTwo
]echo $$levelOne
$levelOne
]echo ${$levelOne}
Thank you xsax! But our Xolar is in another castle!

The parser escapes the quotes and backslashes present in variables before expanding them, to avoid messups in aliases. Though this can sometimes be annoying. It can fortunately be bypassed using the ${var asis} syntax. Example:

]set bar "this is a fancy backslash: \ "
]echo $bar
this is a fancy backslash: \\ 
]echo ${bar asis}
this is a fancy backslash: \

Another example showing why this escaping makes aliases safer:

]alias foo "echo First parameter: ${1 asis}   Second parameter: ${2 asis}"
]alias bar "foo \"${1 asis}\" \"${2 asis}\""
]bar "One One" "Two Two"
First parameter: One One Second parameter: Two Two 
]bar "One \"One" "Two Two"
First parameter: One Second parameter: One"

Can anyone find a better/simpler example?

As you can see, the second time I called “bar” with an “infected” string, the alias messed up. It would have been safe without using “asis”.