# Writing Windows CMD Batch File Stuff

I hope I never have to write another Windows .BAT file again in my life, but if I don't jot this stuff down, I will forget it, and then I will.

## Subroutines

1. Use `:somelabel` to define a block of code.
1. Use `call :somelabel` to jump to a defined label, run that block of code to the end, then return.
2. Use `goto :label` to jump to that label.
3. Put `:eof` at the end of your file.

So,

```
if (some error) do (
echo nope, you messed up
goto :eof
)

for (whatever) do (
call :myprocess
)
goto :eof

:myprocess
echo do stuff here
:eof
```




## Looping over an input file

https://stackoverflow.com/questions/10653371/how-do-i-get-a-batch-file-to-accept-input-from-a-txt-file

```
for /f %%a in (a-file-with-one-thing-per-line.txt) do (
echo Here's the line: %%a
)
```

## Get the filename out of a URL

https://stackoverflow.com/questions/9252980/how-to-split-the-filename-from-a-full-path-in-batch

## "if not exist"

https://stackoverflow.com/questions/23735282/if-not-exist-command-in-batch-file

I used this to determine if a program was installed (I'm sure there's some better wiz-bang way to check the registry for it...)

```
:: Check if chrome is in the right place
if not exist "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" (
echo You don't have Chrome installed in "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe"
goto :eof
)
```

## Number of command-line arguments

https://stackoverflow.com/questions/1291941/batch-files-number-of-command-line-arguments

There's not something like `$#` in bash, so there's a whole level of hell involving looping and/or a bunch of GOTOs.

I wanted to check if there were *no* arguments; you can do this:
```
if "%1"=="" (
echo You need to pass at least one parameter, sorry.
goto :eof
)
```

## Slashes to dashes

```
rem change slashes to dashes in the first parameter passed
SET _test=%1
SET _result=%_result:/=-%
```

That second line is replacing one string with another, so you can do stuff like this, too:
```
SET _result=%_result:pepsi=coke%
```

For lots more of this https://www.dostips.com/DtTipsStringManipulation.php

Related: https://gist.github.com/jkonrath/fb471f4d15947555af254c877ca04d53

## Make a timestamped file

I covered this over here: https://gist.github.com/jkonrath/25188b7d8d59cd55b5843e0e557c06c6

## Disclaimer

I have no idea what I'm doing. I learned all of this by brute force. It worked for me, but it might not work for you, and it's probably not the best way of doing things.

This was all done on Windows 10 circa 2020. I don't use Windows daily anymore, so for all I know, you have to buy each command in the app store at this point.

Also I just realized I don't even have a machine to test these anymore, so caveat emptor.