Redirect the output of a for loop in cmd.exe

Question

What I want to do is this:

(for %%a in ('command') DO something) | anothercommand

Unfortunately cmd.exe parses parentheses like this:

v open                v close
(for %%a in ('command') DO something) | anothercommand 

If I don't use parentheses around for , then the anothercommand is treated as if it was in the DO block.

This forces me to output the result of each DO block iteration to a temporary file and then read it again:

for %%a in ('command') DO echo %%a >> file.txt
anothercommand < file.txt

I'm looking for a cleaner solution that doesn't bottleneck itself because of writing and reading from storage.

Answer 1

Your assumption is wrong, cmd.exe does NOT close the first parenthesis after your command.
There is another problem in your code.

Working example:

( FOR /F "delims=" %%A in ('dir') do @echo ##File: %%A ) | findstr /N "^"

But the main problem of piping is, that both sides are executed in a new sub cmd.exe instance.
And there it's running in the command line context, not batch file context.
Therefore the syntax changes a bit, and it's necessary to add the @ in front of echo to avoid the debug output.