Multiple members are allowed in a gzip file

demo.md

A gzip (.gz) file typically contains a single member, but as per RFC 1952 it can contain many members.

2.2. File format

A gzip file consists of a series of "members" (compressed data sets)

GNU gzip and Apple gzip both appear to decompress multiple members to a single output file.

Demo

1. Create some test files

   $ echo foo > foo.txt
   $ echo bar > bar.txt

2. Individually gzip them (which deletes the originals)

   $ gzip foo.txt
   $ gzip bar.txt

3. Concatenate the invidiual gzip files into a combined gzip

   $ cat foo.txt.gz bar.txt.gz > foobar.gz

4. Delete the indiduals, leaving only the combined gzip

   $ rm foo.txt.gz bar.txt.gz
   $ ls -l 
   total 1
   -rw-r--r-- 1 alex alex 64 Sep  5 10:48 foobar.gz

5. gunzip the combined, contents of both original files are written to a single uncompressed output file

   $ gunzip foobar.gz
   $ ls -l
   total 1
   -rw-r--r-- 1 alex alex 8 Sep  5 10:48 foobar
   $ cat foobar
   foo
   bar