GREP Print Blank Lines For Non-Matches

Solution 1:

You can use

#!/bin/bash
s='This is very new
This is quite old
This is not so new'
sed -En 's/.*This(.*)new.*|.*/\1/p' <<< "$s"

See the online demo yielding

 is very 

 is not so 

Details:

• E - enables POSIX ERE regex syntax
• n - suppresses default line output
• s/.*This(.*)new.*|.*/\1/ - finds any text, This, any text (captured into Group 1, \1, and then any text again, or the whole string (in sed, line), and replaces with Group 1 value.
• p - prints the result of the substitution.

And this is what you need for your actual data:

sed -En 's/.*"user_ip":"([^"]*).*|.*/\1/p'

See this online demo. The [^"]* matches zero or more chars other than a " char.