One day, a vendor told me they couldn't push updates to staging because the release pipeline was failing while extracting ZIP artifacts.

The error looked like this:

i" -C "...\extracted" was unexpected at this time.
Cmd.exe exited with code '255'.

At first glance, the command looked fine:

for /r "drop" %i in (*.zip) do tar -xf "%i" -C "drop\extracted"

The part I'd missed was where the command was running. On Windows, Azure DevOps Command Line tasks put inline scripts into a temporary .cmd file. The Microsoft task documentation describes this behavior.

Windows CMD uses %i for a FOR variable in an interactive session, but %%i in a batch script. That applies both when declaring the variable and when using it inside the loop.

So the corrected script was:

if not exist "drop\extracted" mkdir "drop\extracted"
for /r "drop" %%i in (*.zip) do tar -xf "%%i" -C "drop\extracted"

Here, drop is relative to the task's working directory. This assumes the Windows agent has a tar executable that supports ZIP extraction and that the output directory is dedicated to these artifacts. Archives with matching filenames can overwrite each other's extracted files.

After changing both occurrences to %%i, the deployment succeeded.

It was a small difference, but one I'll remember the next time a command works in a terminal and fails in a pipeline.

Hope you found this useful!