grep commands patterns and metacharacter classes In Linux escape "\" character importance

 

cat /etc/oratab | grep -e "^[\a-Az-Z0-9\]\{0,8\}\:*/[[:graph:]]*"

Hints:-

Always use caret "^" and "$" without escape "\"  like  "^[[:digit:]]"  or "$[[:digit:]]" .

To include forward search use "\+" or "*"  like "^[[:graph:]]\+" or "^[[:digit:]]*" .