grepping using the result of previous grep

Question

Is there a way to perform a grep based on the results of a previous grep, rather than just piping multiple greps into each other. For example, say I have the log file output below:

ID 1000 xyz occured
ID 1001 misc content
ID 1000 misc content
ID 1000 status code: 26348931276572174
ID 1000 misc content
ID 1001 misc content

To begin with, I'd like to grep the whole log file file to see if "xyz occured" is present. If it is, I'd like to get the ID number of that event and grep through all the lines in the file with that ID number looking for the status code.

I'd imagined that I could use xargs or something like that but I can't seem to get it work.

grep "xyz occured" file.log | awk '{ print $2 }' | xargs grep "status code" | awk '{print $NF}'

Any ideas on how to actually do this?

Answer 1

A general answer for grep-ing the grep-ed output:

grep 'patten1' *.txt | grep 'pattern2' 

notice that the second grep is not pointing at a file.

More about cool grep stuff here

Answer 2

You're almost there. But while xargs can sometimes be used to do what you want (depending on how the next command takes its arguments), you aren't actually using it to grep for the ID you just extracted. What you need to do is take the output of the first grep (containing the ID code) and use that in the next grep's expression. Something like:

grep "^ID `grep 'xyz occured' file.log | awk '{print $2}'` status code" file.log

Obviously another option would be to write a script to do this in one pass, a-la Ed's suggestion.