post-build event with multiple if/copy combinations only execute if first file does not exist

Question

Given the bin\ directory inside the Delphi project contains the files Cert.pem and Key.pem, the below Delphi post-build event only copies both files if C:\Binaries\Cert.pem does not exist:

if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR))
if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR))

As soon as C:\Binaries\Cert.pem exists, the Key.pem file is never copied.

How can I solve this in the post-build event?

Edit: unlike my 2014 post, this is indeed possible using parentheses. See my answer below.

Jeroen Wiert Pluimers Jeroen Wiert Pluimers · Accepted Answer · 2018-07-17T18:53:33

The problem with Delphi post-build events is that they are not batch files.

It means that statements that look like lines are being concatenated by the Delphi IDE into one big & ampersand separated statement. This ensures the commands are executed in sequence, as per Command Redirection, Pipes - Windows CMD - SS64.com:

commandA &  commandB      Run commandA and then run commandB

So this is the actual statement that gets executed:

if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR))&if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR))

The problem here is that now the second if is seen as a continuation of the "then" part of the first if statement: the second if never executes when the $(OUTPUTDIR)Cert.pem exists.

What helps is a little known feature that you can wrap each command inside parentheses. Normally this is to allow one command to span multiple lines (especially for if, and for..do loops), but it also works on one line.

Wrapping each line having an if statement inside parentheses ensures they become standalone statements not affecting the other lines, even if they are being concatenated with & ampersand separators.

In the dialog it looks like this:

(if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR)))
(if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR)))

That way, the IDE translates it into one statement:

(if not exist $(OUTPUTDIR)Cert.pem (copy bin\Cert.pem $(OUTPUTDIR)))&(if not exist $(OUTPUTDIR)Key.pem (copy bin\Key.pem $(OUTPUTDIR)))

Now it works as intended:

When $(OUTPUTDIR)Cert.pem exists but $(OUTPUTDIR)Key.pem does not, only $(OUTPUTDIR)Cert.pem is copied
When $(OUTPUTDIR)Cert.pem does exists but $(OUTPUTDIR)Key.pem does, only $(OUTPUTDIR)Key.pem is copied
when neither exist, both are copied
when both exist, neither are copied

I did not know this "trick" when writing my 2014 post Delphi prebuild/prelink/postbuild events, so I need to write an update for it.

Searching for batch file parentheses site:microsoft.com -site:social.technet.microsoft.com -site:answers.microsoft.com did not reveal it in the official documentation, but I am not surprised as it grew hysterically, instead of being designed. Or like the Old New Thing attributes h2g2:

Much like the universe, if anyone ever does fully come to understand Batch then the language will instantly be replaced by an infinitely weirder and more complex version of itself. This has obviously happened at least once before ;)

The best documentation I could find was at Parenthesis/Brackets - Windows CMD - SS64.com:

Parenthesis can be used to split commands across multiple lines. This can make code more readable. Variables will be evaluated for the code block just as if the command was a single line.
 (command)

 (
  command
  command )
Things that break inside parenthesis The CMD shell does not use any great intelligence when evaluating parenthesis, so for example the command below will fail:
IF EXIST MyFile.txt (ECHO Some(more)Potatoes)
...

post-build event with multiple if/copy combinations only execute if first file does not exist

2 Answers