How to add a different prefix to every line in a grep output?

Question

I currently have this code:

cat /proc/cpuinfo | grep "MHz" | cut -d ':' -f2 | sed 's/.*/Core NUM&Mhz/'

Which outputs the following (for 8 cores):

Core NUM 1941.054Mhz
Core NUM 1949.820Mhz
Core NUM 2022.734Mhz
Core NUM 1877.171Mhz
Core NUM 1938.265Mhz
Core NUM 1945.703Mhz
Core NUM 1845.562Mhz
Core NUM 1781.546Mhz

What I want to do is replace "Core NUM" with actual numbers (e.g. Core 0, Core 1, Core 2, Core 3...) I would prefer a solution that can be done on one line with the rest of this command, but since I am in the end working from a bash script, I don't mind a multi-line/scripted solution either. The biggest problem I guess is that grep is one command outputting many lines, and I don't know if there's a way to target these lines one by one in something like a for or while loop.

So, how can I do this?

Answer 1

Let awk do it all for you:

</proc/cpuinfo awk -F : '/MHz/{printf "Core %d%sMhz\n", n++, $2}'

Answer 2

cat /proc/cpuinfo | awk '/MHz/ {print "Core", i++, $NF "Mhz"}' gives,

Core 0 800.000Mhz
Core 1 800.000Mhz

Answer 3

I did a slightly different awk version, but once you are familiar with awk, it will stand out as the natural solution for this. I used the following:

cat /proc/cpuinfo | awk -F : '/^processor/ { x = $2 } /^cpu MHz/ { print "CPU" x ":" $2 " MHz" }'

which uses a slightly different approach of saving off the value of the 'processor' field and then recalling it when the cpu MHz field is encountered. You can do slightly more general things this way, provided you know which of the fields you are interested in occurs last. In this case, we know the 'cpu MHz' comes after the 'processor' field, so we know that when 'cpu MHz' is encountered, the value stored in the variable x will be correct.

Output looks like:

CPU 0: 887.597 MHz
CPU 1: 818.359 MHz
CPU 2: 887.597 MHz
CPU 3: 803.222 MHz