Shell Programming and Scripting

attr1=sample,attr2=sample,attr3=sample,email=example@example.org;
EMAIL=example@example.org,attr3=sample,attr4=sample,attr5=sample,
EMAIL=example@example.org,attr5=sample,attr6=sample,email=example@example.org...

grep -Poi email:\K.*?(?=;|$)'

email=xxx
email=xxx
email=xxx

email=xxx, email=xxx, email=xxx

awk -F, '{for(i=1;i<=NF;i++){if(tolower($i) ~ /email/){A=A?A OFS $i:$i}};print A;A=""}' OFS=,  Input_file

email=example@example.org;
EMAIL=example@example.org
EMAIL=example@example.org,email=example@example.org

sed 's/^/,/;:B;s/,[^eE][^mM][^aA][^iI][^lL][^,]*,/,/g;tB;s/^,//;s/[[:punct:]]$//' file
email=example@example.org
EMAIL=example@example.org
EMAIL=example@example.org,email=example@example.org