I want to gzip two or more files into one file, I checked this and this but both have files like: n1.txt, n2.txt, ... but my filenames are completely different, like: file.mp4, bar.txt, foo.jpeg and I want to gzip them all and put the output into one file. This didn't help too:

gzip -c file.mp4 > test.gz

gzip -c bar.txt >> test.gz

Do I have to tar them first?

And another question: In tar files, we can watch inner files without decompression using:

tar -tvf filename.tar

Is there anyway to do this with gzip or bzip2?

Unlike ZIP, RAR or 7-Zip, for example, gzip can only compress one file. As you’ve already noted, there is the tar program which can serialize multiple files into one which makes them ready for gzip. The traditional Unix philosophy prefers to use multiple simpler and more specialized tools than one monolithic and complicated. In this case, it results in using tar and gzip consecutively, resulting in a .tar.gz (or .tgz) file.

However, GNU tar includes the -z option which compresses the result of the traditional tar using gzip in just one command.

.tar.gz files are mostly created using the -czvf options:

• 
  create a new archive


• gzip (alternatives: j for bzip2, J for xz)


• 
  verbose (list processed files; optional)


• output file (the following argument specifies the output file)

In your example, you can use the command:

tar -czvf test.tar.gz file.mp4 bar.txt

Is there any way to watch inner files without decompression with gzip or bzip2?

Yes, your command also works for a .tar.gz file:

tar -tvf test.tar.gz

Further reading

• GNU TAR Manual page


• 10 quick tar command examples to create/extract archives in Linux

gzip is a compressor, not an archiver, but it works well with tar

tar -cvzf file.tar.gz path-to-files-or-directories-to-compress

See man tar

Compression options

   -a, --auto-compress

          Use archive suffix to determine the compression program.



   -I, --use-compress-program=COMMAND

          Filter data through COMMAND.  It must accept the -d option,  for

          decompression.  The argument can contain command line options.



   -j, --bzip2

          Filter the archive through bzip2(1).



   -J, --xz

          Filter the archive through xz(1).



   --lzip Filter the archive through lzip(1).



   --lzma Filter the archive through lzma(1).



   --lzop Filter the archive through lzop(1).



   --no-auto-compress

          Do not use archive suffix to determine the compression program.



   -z, --gzip, --gunzip, --ungzip

          Filter the archive through gzip(1).



   -Z, --compress, --uncompress

          Filter the archive through compress(1).

And yes, you can watch compressed archives the same way.