Validating emails in file with batch - regex

Question

I have a file with emails and I need to validate them.
The sequence is:
First name.
Dot.
Last name.
Number (optional - for same names).
static string domain(#utp.ac.pa).
I wrote this:
egrep -E [a-z]\.+[a-z][0-9]*#["utp.ac.pa"] test.txt
It should match this email: "anell.zheng#utp.ac.pa"
But it is also matching:
test4#utp.ac.pa
2anell#utp.ac.pa
Although they don't follow the sequence. What am I doing wrong?

Answer 1

Your regex doesn't even match the first email. If I understand your requirements correctly, this should work:
[A-Za-z]+\.[A-Za-z]+[0-9]*#utp\.ac\.pa
Note that to match a dot, it needs to be escaped (i.e., \.) because . matches any character.
You can get rid of A-Z if you don't want to match upper-case letters.
Try it online.
Let me know if this isn't what you want.

Answer 2

Regex: ^[A-Za-z]+\.[A-Za-z]+(?:_\d+)*#utp\.ac\.pa$
Demo
Regex Details:
^ asserts position at start of a line
Match a single character present in the list below [A-Za-z]+
. matches the character . literally (case sensitive)
Match a single character present in the list below [A-Za-z]+
Quantifier — Matches between one and unlimited times, as many times as possible, giving back as needed (greedy)
Non-capturing group (?:_\d+)*
Quantifier — Matches between zero and unlimited times, as many times as possible, giving back as needed (greedy)
_ matches the character _ literally (case sensitive)
\d+ matches a digit (equal to [0-9])
Quantifier — Matches between one and unlimited times, as many times as possible, giving back as needed (greedy)
#utp matches the characters #utp literally (case sensitive)
. matches the character . literally (case sensitive)
ac matches the characters ac literally (case sensitive)
. matches the character . literally (case sensitive)
pa matches the characters pa literally (case sensitive)
$ asserts position at the end of a line