~Basic Batch File Tips Using '%' Arguments in Batch Files - By Simon Burrows `If you've ever had the job of writing any but the simplest of `batch files before, you will have used arguments. Incorporating `these into such a batch file allows the user of the file to `specify one or more commands as well as the name of the .BAT file `at the Command Line. If you have never heard of arguments `before, or do not know how to use them, read on. This documents `contains a brief(ish) description of them and their uses :- ~`컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� `When using many of the utilities DOS comes with (eg, FORMAT.COM) `you must specify more than just the name of the file at the `command line. For example, when using FORMAT.COM, you may type `this to format a disk in drive A: to 3.5" HD :- ~FORMAT A: /F:1.44 `This is exactly the same for many batch files. `For example, many older games available must be installed to a `hard disk with the use of a Batch File installation program. You `may need to type something like this at the command line to `install a game on a disk in drive A: to a directory called `SOLITARE on drive C: :- ~INSTALL A: C:\SOLITARE `When we do this, each part of the command is called an argument. `Whenever there is a space (eg, in between A: and C:\SOLITARE) a `new argument begins. These arguments can also be called `variables. `Each argument, or variable, is remembered by your computer as a `'%' sign and a number. So, the separate parts of the example `above are named as follows :- ~`INSTALL A: C:\SOLITARE ` � � � ` � � � ~` %0 %1 %2 `The part called '%1' is the first argument even though it is `really the second, after '%0'. Most of the time you will never `use '%0', although, as you will see later in this text, it has `some uses. `If you are just using batch files, you needn't worry about these `'%' sign 'abbreviations' but they are an important part of the `writing of a batch file. `As an example, imagine you had a batch file which copies a file `from one disk to another. At the command line you specify where `the file is located at the moment and then its destination. For `example, you might type the following at the command line :- ~COPYIT A: C: `The batch file, COPYIT.BAT, would use DOS's Copy command to copy `the program. However, if you listed the file, it wouldn't just `read something like "COPY FILE.EXE A: C:" because this will `only copy the file from one set disk drive (A:) to another set `disk drive (C:). Instead, it would read something like this :- ~COPY FILE.EXE %1 %2 `If you loaded this batch file now, stating the two arguments at `the command line to specify where the file for copying is now, `and where you want it to go, (eg, COPYIT A: C:), your computer `will replace the '%1' in the batch file with the first argument, `and the '%2' with the second argument. This means that you could `use this same batch file to copy the file "FILE.EXE" regardless `which drive it is on and which drive you want it to be copied to. `For example, if you typed :- ~COPYIT F: Y: `...your computer would automatically replace the %1 in `COPYIT.BAT's listing with 'F:' and the %2 with 'Y:' so it would `copy the file called 'FILE.EXE' from a disk in drive F: to a disk `in drive Y: (Just as long as you had these drives available on `your PC, of course!) `You could incorporate the use of variables and the IF command to `display a help message to the user of the batch file. For `example, in our example of "COPYIT.BAT", you could make it so `that if your user specified the first variable as '/?' (by `typing "COPYIT /?") a message would be displayed describing what `the file "COPYIT.BAT" does. `To do this you might use the following batch file listing :- ~`IF "%1"=="/?" GOTO HELP ~`COPY FILE.EXE %1 %2 ~`GOTO END ~`:HELP ~`ECHO The file "COPYIT.BAT" will copy the file called "FILE.BAT" ~`ECHO from any drive to a destination of your choice. ~`ECHO. ~`ECHO Usage is as follows :-ECHO. ~`ECHO COPYIT [Location of "FILE.EXE] [Destination of "FILE.EXE] ~`:END `The top line of this is saying that if the user specifies the `first argument as '/?' (ie, by typing "COPYIT /?") then your `computer should go straight to the section of the batch file `called "HELP". This is the part directly after the ":HELP" line, `and has a series of 'ECHO' lines to display a text message. `However, if the user does not specify the first argument as '/?' `and instead types something like "COPYIT A: C:", then %1 will not `be '/?' so this first line will be ignored and it will go to the `next line. The next line, as described above, copies the file, `then, the line after that tells your computer to skip to the `section called "END" at the end of the file so it misses out the `unwanted help message. `So, if your user types "COPYIT X: Y:" the file "FILE.EXE" is `copied from disk X: to disk Y:, and if they type "COPYIT /?" the `following text-message is displayed :- ~`The file "COPYIT.BAT" will copy the file called "FILE.BAT" ~`from any drive to a destination of your choice. ~`Usage is as follows :- ~`COPYIT [Location of "FILE.EXE"] [Destination of "FILE.EXE"] `But what happens if your user doesn't specify any argument, and `instead loads the batch file by typing simply "COPYIT"? Well, if `this is the case then your computer will not know where the file `is and where to copy it to. In this eventuality you will need a `message displayed which tells the user that they have loaded the `file wrongly. This message might as well be the same as the one `displayed if they type "COPYIT /?" as this message (if your is `the same as mine, anyway) includes information on how to load `the file properly. `However, there's a problem. The ONLY way this message can be `displayed is if the file COPYIT.BAT is loaded with the '/?' `argument. Because of this, the only way to get the message to be `shown if no argument is specified is to make your computer reload `the batch file with the '/?' argument automatically. `To do this we need use of the '%0' argument mentioned at the `start of this document. Since '%1' stands for the first argument `after the filename, '%0' stands for the filename itself. This `means that you could put %0 into your batch file and the file `will reload when this figure is reached. `So, what we can do is say that if there is no '%1' specified, `then the batch file should be reloaded by the computer, this time `with the argument '/?', so that the message is displayed showing `the user how to use the batch file properly. By adding this feature to our batch file, it now reads :- ~`IF "%1"=="" %0 /? ~`IF "%1"=="/?" GOTO HELP ~`COPY FILE.EXE %1 %2 ~`GOTO END ~`:HELP ~`ECHO The file "COPYIT.BAT" will copy the file called "FILE.BAT" ~`ECHO from any drive to a destination of your choice. ~`ECHO. ~`ECHO Usage is as follows :- ~`ECHO. ~`ECHO COPYIT [Location of "FILE.EXE"] [Destination of "FILE.EXE"] ~`:END `The first line checks to see whether there are no arguments `specified. It does this by seeing whether '%1' equals nothing `("" means nothing) rather than whether it exists at all. If '%1' `does equal nothing, it carries out the rest of the line (the `"%0 /?" part) which tells your computer to reload the batch file `with '/?' as the one and only argument. Otherwise, it skips this `part and continues to line two. So with this batch file, there could be 3 outcomes :- `1. The file is loaded with the first argument as the curent drive ` of the file for copying, and the second as the file's ` destination. In this case, the file will be copied correctly. `2. The file is loaded with the first and only argument being ` '/?'. In this case, the text message is displayed quickly ` explaining the file and how to use it properly. `3. The file is loaded with no arguments. In this case, the same ` text message is displayed quickly explaining the file and how ` to use it properly. ~`Well, there you go then folks, have fun!.. ` 컴컴컴컴컴컴컴� ~` Simon Burrows ` 컴컴컴컴컴컴컴�