Since Windows 2000 you can use subroutines (depending on the understanding and definition of "function" and "procedure", one can also refer to them as "procedures", that can manipulate both local and global variables and don't return any value ("void")).

Basically, a subroutine is a number of commands between a label and a GOTO:EOF statement.

GOTO:EOF is often written without a space, as it is used as a special GOTO command: It jumps to the End of File, thus ending the currently executed script.

That is the reason why a subroutine is not called with GOTO :MY_SUBROUTINE, but with

This executes the current batch AGAIN in the current context, but jumps immediately to the given label. And that is the reason why ending the script at the end of the subroutine - it just ends the execution started through the CALL command.

A subroutine has its own parameters, you don't have access to the "parent" batch parameters unless they were stored in an environment variable.

You can see that there is another GOTO:EOF after the CALL command. You don't want your first subroutine being executed after your script finished, do you? This is the basic structure of a batch script using subroutines:


What about the local context I mentioned at the beginning? That does not differ from standard batch scripts:


As subroutines do not provide a way of returning any value (and, of course, there is no direct way to store the result of an execution in a variable), here is what I do. By convention, I reserve the global variable %RESULT% for storing the result of the last called subroutine that should return a value. You can think of it like putting a value onto a one-element stack.

This won't work if using local context within the subroutine, however due to the cmd.exe-nature there is way to preserve a variable after ending the local context:

A little explanation: As the batch reads a full line, expands all variables, parses the line and then finally executes all contained commands in order, the important line looks like this after expansion:
See, variable preserved and available in global context. Sometimes you want to preserve more than one variable, so you add additional SET statements. But be careful and do not insert a space before the ampersand - that space will contained in your variable!

A little advise at the end: document your subroutines, otherwise you won't know what parameters it takes, what global variables it manipulates or requires or what value it "returns". I use double colons for subroutine documentation.

See also this article about handling parameters and variables containing special characters.