This is just for the sake of an example of finding $foo that occurs after $bar. Substitute ifconfig and the arguments of grep appropriately for your use case.

• In the output of ifconfig there are several lines with inet. We want to get to the first one that comes after a line starting with en1
• grep ^en1 -A5 will print the line starting with en1 and the next 5 lines that follow it
• grep inet will print only the lines matching inet
• head -n 1 will print only the first line

The value 5 in -A5 is really just a guess that the line we're interested in will be within the next 5 lines, the appropriate number depends on your use case.

Kind of a dumb technique, but it's easy to remember.