flatten a gnu tar archive

Problem:

I have a tar file with a deep directory hierarchy but only some files in it. I want to extract the files into my current directory and not care for subdirectories. Filenames do not conflict. The gnu tar option --remove-components does not handle this well.

Solution:

Fortunately, there is a very general gnu tar option --transform:

    tar --extract --transform='s/.*\///' --show-transformed-names --file=foo.tar

This deletes pathname up to the first slash character, resulting in the desired effect.

Example:

$ mkdir -p a/b/c/d/e/f/g/h/i
$ echo "hi there" >  a/b/c/d/e/f/g/h/i/foobar
$ tar cvf foo.tar a
a/
a/b/
a/b/c/
a/b/c/d/
a/b/c/d/e/
a/b/c/d/e/f/
a/b/c/d/e/f/g/
a/b/c/d/e/f/g/h/
a/b/c/d/e/f/g/h/i/
a/b/c/d/e/f/g/h/i/foobar
$ tar --extract --transform='s/.*\///' --show-transformed-names --verbose --file=foo.tar
a
b
c
d
e
f
g
h
i
foobar
$ cat foobar
hi there