Exclude pattern in a Grep using extended regex

Question

I got a Grep that is killing me

Let's suppose i got the a file (file.xml) with the two below entries:

pos_ADF_datasource-1450-jdbc.xml
datasource-1450-jdbc.xml

Now If i run the below grep:

grep -E '(ADF)' file.txt

I got the below output:

pos_ADF_datasource-1450-jdbc.xml

Now i want to exclude ADF to get the other entry, it should be easy, but i tried it all and I'm unable to let it works:

grep -E '(?<!ADF)' file.txt

I tried many but i'm sure there is something i'm not considering that is making my expression not working...

I need and want to use the -E, i know it works not using the extended regex!

Please guys me light me!

RESOLVED:

Thanks Wiktor for the below consideration:

ERE POSIX does not support lookarounds. Even if you use -P excluding 'ADF' it will just match any position that is not preceded with ADF

You cannot check with an ERE regex if a string does not contain a pattern. Only if it is not equal, does not start/end with a pattern. You may only do it with a PCRE regex. grep -P '^(?!.*ADF)' file.txt

Then i figured it out with grep -Pe:

grep -Pe "^((?!.*ADF).)*-jdbc.xml$" file.xml

I know, but why it does not work if i just use -E that should just mean that i'm using an extended regex.. — ivoruJavaBoy, May 22 '17 at 11:10
ERE POSIX does not support lookarounds. Even if you use `-P '(?<!ADF)'` it will just match any position that is not preceded with `ADF`. Not what you need, right? — Wiktor Stribiżew, May 22 '17 at 11:12
Okay got it, but what about exclusions? Can't I manage exclusion with -E ?!? I mean, let's say i want just say "with -E" get all the lines that does not contain "ADF" — ivoruJavaBoy, May 22 '17 at 11:31
No, you cannot check with an ERE regex if a string does not *contain* a pattern. Only if it is not equal, does not start/end with a pattern. You may only do it with a PCRE regex. `grep -P '^(?!.*ADF)' file.txt` — Wiktor Stribiżew, May 22 '17 at 11:35

Exclude pattern in a Grep using extended regex

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