Question

So I have been trying to figure this out for a while, but nothing came to me. I have narrowed it down to a small case, so please let me know your thoughts.

I have a directory of files (1-a.txt and 1-b.txt) and a batch file like this:

for %%X in (1) do ^
fc %%X-a.txt %%X-b.txt > tmp.txt &^
if errorlevel 0 (echo 5) else (echo 6) &^
echo 7

Basically, I want it to echo 5 if the files are the same and 6, 7 if they are different.
However, it ALWAYS echos 5. Echo 7 is ignored entirely.

Any thoughts?

Answer 1

if errorlevel is true when the error level is at least 0. It’s always a greater than or equal comparison:

C:\>help if
Performs conditional processing in batch programs.

...

  ERRORLEVEL number Specifies a true condition if the last program run
                    returned an exit code equal to or greater than the number
                    specified.

Usually you can just switch the branches around:

if errorlevel 1 (echo 6) else (echo 5)

In your case I’d also advise you to use parentheses to group statements:

for %%X in (1) do (
  fc %%X-a.txt %%X-b.txt > tmp.txt
  if errorlevel 1 (echo 6) else (echo 5)
  echo 7
)

As another option to the explicit if after the program call there are also operators that run another command depending on the outcome of the previous one:

fc %%X-a.txt %%X-b.txt > tmp.txt && echo 5 || echo 6