Console Script Grammar: Difference between revisions

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Revision as of 23:07, 9 September 2017

Con files are the core of how Battlefield 2 (and 1942 before it) configures its weapons, maps, objects, players and other game assets. With Battlefield 2, the con grammar has extended into a rudimentry scripting language, with loops and full conditionals. Battlefield 1942 had only very rudimentry conditionals.

Comments

There exist two classes of comments, block:

 beginRem
 this text is ignored
 endRem

and line:

 rem this text is ignored

Statements

Statements are a command followed by a number of optionally "quoted", whitespace-seperated arguments. The number of arguments may be variable or strictly limited by the command in use. The available commands is beyond the scope of this page, but a good portion of them are included with the editor. A full list is available by running GNU strings against your bf2.exe ;)

Variables

Variables must be predefined, and have a strict naming system. All mutable variables must begin with v_ whereas all immutable variables or constants must begin with c_. It's a simple form of wikipedia:Hungarian Notation.

Mutable Variables

The code:

 var v_dongs = test

Defines a new variable called dongs or v_dongs depending on your point of view with the value "test". When defining a variable you can omit the default value however:

 var v_dongs

is a value construct for example.

Immutable Variables

 const c_butts = test

Defines a constant called, again, butts or c_butts with the value "test". Obviously, this variable cannot be changed.

const vs. var and assignments

Assigning to a variable is as simple as appending -> v_varname to any command. However, many commands do not return a value. The ones that do generally return either a boolean value (0 or 1) or a simple string.

Clearly, trying to assign to a const variable is an error and will not work.

Conditionals

Conditionals include the standard if ... endIf, if ... elseIf ... endIf and while ... endWhile constructs. These evaluate an expression.

Expressions

The grammar of an expression is roughly:

 <variable> <comparator> <value>

Where

  • variable is any variable name beginning with v_ or c_.
  • comparator is one of ==, !=, >, >=, < or <= or their textual equivalents: lessOrEqualThan, lessThan, greaterOrEqualThan, greaterThan, notEquals, equals.
  • value is any literal string, quoted if neccessary.

Return

You may cease interpretation of the current .con file by using the command return. This resumes interpretation from the calling file. It is an error to use this unless the file was called with...

include and run

include and run do similar things and may in fact be identical. These trigger the interpretation of another .con file. They also have the ability to set arguments, which are a special type of mutable variable. For example:

 run test.con 1 2 3

Runs test.con. In test.con, the variables v_arg1, v_arg2 and v_arg3 are set to 1, 2 and 3 respectively. Typically this is used along with a conditional to do something for the editor mode, or to do something different for single player mode (a common use in BF1942, where this method also existed).

An Example

 var v_tst
 fileManager.fileExists movies/menu.bik -> v_tst
 if v_tst == 0
 fileManager.copyFile ../../mods/bf2/movies/menu.bik movies/menu.bik
 fileManager.copyFile ../../mods/bf2/movies/menu_loggedin.bik movies/menu_loggedin.bik
 endIf

This example checks if movies/menu.bik exists, and if it doesn't copies two files from the bf2 mod to the current mod.