Findstring in a loop ?

ETC Microsoft Windows
1

Well, I have a txt that looks like this:

Image: 0001.gif
comment: Lavc54.63.100
    date:create: 2014-06-21T19:22:02+02:00
    date:modify: 2013-03-07T22:24:23+01:00
    signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed
Image: 0002.gif
comment: Lavc54.63.100
    date:create: 2014-06-21T19:22:02+02:00
    date:modify: 2013-03-07T22:24:23+01:00
    signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed
Image: 0003.gif
comment: Lavc54.63.100
    date:create: 2014-06-21T19:22:02+02:00
    date:modify: 2013-03-07T22:24:23+01:00
    signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed

I know how to use findstr.

In this case I would do this

findstr "Image: " out.txt >> res.txt
findstr signature out.txt >> res.txt

in order to extract the lines Image: and signature.

The problem here is... with this approach it will look like this:

Image: 0001.gif
Image: 0002.gif
Image: 0003.gif
signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed
signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed
signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed

I'd however want it to look like this

Image: 0001.gif
signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed
Image: 0002.gif
signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed
Image: 0003.gif
signature: 32feab76ef7f9b15baef90406c4021c0927862ffacd5ea82ba9337e9a01e80ed

Is it possible to utilize findstring and output those like this ?

2

Try

findstr "Image: signature:" out.txt >> res.txt
3

Perfect ! Thanks.

BTW:
Let's assume that findstr would only accept "one" parameter:
How would you have solved the problem then ?