How to grep out substring which can change?

Question

Basically I have a very large text file and each line contains

tag=yyyyy;id=xxxxx;db_ref=zzzzz; 

What I want is to grep out the id, but the id

Answer 1

perl -lne 'print $1 if(/id=([^\;]*);/)' your_file

tested:

> echo "tag=yyyyy;id=xxxxx;db_ref=zzzzz; "|perl -lne 'print $1 if(/id=([^\;]*);/)'
xxxxx
>