Unknown output from unix file command

Question

I ran the file command against a file and got this result:

data (gzip compressed data, was <fd:1> from unix)

What does the "<fd:1> from unix" mean?

Answer 1

fd:1 is "file descriptor 1", which means standard output.

My guess is that the file is the result of a pipe from the output of another file like cat file|gzip - > new.gz

I was not able to reproduce that output, but it could be that different versions of gzip handle that differently.