Extract cpio.gz with two archives inside

Question

I've got cpio.gz created with command: cat a.cpio.gz b.cpio.gz > c.cpio.gz

Now i want to extract this c.cpio.gz file to b.cpio.gz and a.cpio.gz. How can i achive that?

Answer 1

OK, I've got 2 .gz files, a.txt.gzand b.txt.gz. Then:

$ cat a.txt.gz b.txt.gz > c.txt.gz
$ hexdump -C c.txt.gz
00000000  1f 8b 08 08 f7 a3 00 59  00 03 61 2e 74 78 74 00  |.......Y..a.txt.|
00000010  4b 2c 4e e1 4a 24 80 01  a9 66 ae 58 24 00 00 00  |K,N.J$...f.X$...|
00000020  1f 8b 08 08 01 a4 00 59  00 03 62 2e 74 78 74 00  |.......Y..b.txt.|
00000030  2b 2c 4f e5 2a 24 0a 73  a5 72 01 00 70 24 d5 0a  |+,O.*$.s.r..p$..|
00000040  2d 00 00 00                                       |-...|

See those 1f 8b 08 starting at 0x00 and 0x20, they are the BOF markers for .gz files (based on the article I referred to in the OP's comments). Now some awk:

$ awk '
BEGIN { RS="\x1f\x8b\x08"; ORS="" }  # set the marker to RS
NR==2 { print RS $0 > "a2.txt.gz" }  # output the marker and what's after first marker
NR==3 { print RS $0 > "b2.txt.gz" }  # output the marker and what's after the second
' c.txt.gz

Produces 2 files and based on my diff they are identical to original files.