Question

grep -E "c.+ features" test.txt

The above works great and is matching call features, etc. However, it is extended pattern.
How do I modify it to a simple pattern and know in general what exactly to escape?

I tried to escape \+ without success.

Answer 1

Escaping + as \+ should work:

$ echo 'call features' | grep -E "c.+ features" 
call features
$ echo 'call features' | grep  "c.+ features" 
$ echo 'call features' | grep  "c.\+ features" 
call features

From the man pages:

Basic vs Extended Regular Expressions

In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions
\?, +, {,
\|, (, and ).