Grep magic

legendary · May 2022

I have this wonder in my logs:

FROM='Mr. Void <[email protected]>'|||ENV_FROM='<[email protected]>'

And this is my parser:

grep -oP "(?<=FROM=\').*?(?=\')"

It does work by bringing me both FROM and ENV_FROM. This is bad. I want EXACT match. Is it possible with lookbehind and lookahead?

Mason · May 2022

@legendary said: This is bad. I want EXACT match.

Is the "FROM" that you're after always at the start of a new line? If so, just change it to:

grep -oP "(?<=^FROM=\').*?(?=\')"

and it won't pick up the "ENV_FROM".

nullnothere · May 2022

Does: grep -oP "(?<=\bFROM=\').*?(?=\')" solve it for you? (I added \b before FROM to signify word boundary and it worked as I think how you'd like it to work - i.e only match FROM and not ENV_FROM).

Here's a sample test case from me:

(the first one is with a capital - not what you want, and the second one is with a lower case - I think what you want).

echo "foo FROM='from_address' bar ENV_FROM='env_from_address' junk suffix\nFROM='Mr. Void <[email protected]>'|||ENV_FROM='<[email protected]>'\nfoo ENV_FROM='hello_how_are_you' bar FROM='howdy' baz" | grep -oP "(?<=\BFROM=\').*?(?=\')"

gives me:

env_from_address
<[email protected]>
hello_how_are_you

And what I think you want is:

echo "foo FROM='from_address' bar ENV_FROM='env_from_address' junk suffix\nFROM='Mr. Void <[email protected]>'|||ENV_FROM='<[email protected]>'\nfoo ENV_FROM='hello_how_are_you' bar FROM='howdy' baz" | grep -oP "(?<=\bFROM=\').*?(?=\')"

gives me:

from_address
Mr. Void <[email protected]>
howdy

legendary · May 2022

@nullnothere said:
Does: grep -oP "(?<=\bFROM=\').*?(?=\')" solve it for you? (I added \b before FROM to signify word boundary and it worked as I think how you'd like it to work - i.e only match FROM and not ENV_FROM).

Here's a sample test case from me:

(the first one is with a capital - not what you want, and the second one is with a lower case - I think what you want).
echo "foo FROM='from_address' bar ENV_FROM='env_from_address' junk suffix\nFROM='Mr. Void <[email protected]>'|||ENV_FROM='<[email protected]>'\nfoo ENV_FROM='hello_how_are_you' bar FROM='howdy' baz" | grep -oP "(?<=\BFROM=\').*?(?=\')"
gives me:
env_from_address
<[email protected]>
hello_how_are_you
And what I think you want is:
echo "foo FROM='from_address' bar ENV_FROM='env_from_address' junk suffix\nFROM='Mr. Void <[email protected]>'|||ENV_FROM='<[email protected]>'\nfoo ENV_FROM='hello_how_are_you' bar FROM='howdy' baz" | grep -oP "(?<=\bFROM=\').*?(?=\')"
gives me:
from_address
Mr. Void <[email protected]>
howdy

Yes, \b did the trick. Thank you for your time and effort. Greatly appreciated.

Grep magic

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