gzip */*.txt

But the extension for each file will be .txt.gz, as gzip uses it to know the original filename.

if you have zip,

zip myzip.zip cvd*.txt

Don't need to tar them first.

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

This uses gunzip to unzip all files in a folder and have the ending .out.gz

gunzip */*.out.gz

This will "loop"* through all folders that have a zipped file in them. Let me add an example:

A
a.out.gz
B
b.out.gz
C
c.out.gz
D
d.out.gz
E
e.out

Using the command above, a.out.gz b.out.gz c.out.gz d.out.gz will all get unzipped, but it won't touch e.out since it isn't zipped.

*this is called globbing or filename expansion. You might like to read some more about it here.

You can use below command.

Go to the directory where your .gz file is and run command:

for f in *.gz ; do gunzip -c "$f" > /home/$USER/"${f%.*}" ; done

It will extract all file with original name and store it to current user home directory(/home/username). You can change it to somewhere else.

EDIT :

gunzip *.gz

This command also will work. But, by default, it replaces original file.