Curl -K - works fine, but with -Z it outputs some zero length files

I have a script in which I have a pipe that I've made output a series of:

url="..."
output="..."

that pipe into a curl command:

curl -K - lots of other options

If I have the curl command as above, it downloads one file at a time and it works just fine.

However, if I attempt to have curl run them in parallel by specifying -Z, then it creates many of the downloaded files with zero length. This happens even if I specify --parallel-max=1 which you might think is the same as running one at a time, but it seems not.

Any idea what is going on, and how to debug this?

1 Answer

There's a bug that is fixed in version curl 7.70.0 which causes this problem. The current version shipped with Ubuntu 20.04.2 LTS is 7.68.0, so it needs to be updated either by building it yourself, or waiting for ubuntu to do so.