Newbie grep question.... output is doubled

Question

I have been teaching myself bash scripting and I wanted to write a script that makes a txt file with specific hardware information. I figured that 'grep' would be a great tool for pulling the info I wanted from /proc and other places.

My issue is the output is doubled. What am I doing wrong?

$ grep "Mhz" /proc/cpuinfo
cpu MHz     : 1200.000
cpu MHz     : 1200.000

$ cat /proc/cpuinfo | grep "MHz"
cpu MHz     : 1200.000
cpu MHz     : 1200.000

....I do understand that the commands above will not redirect into my txt file. I am trying to get the command to output what I want before redirecting.

Answer 1

You have two CPUs, or at least two cores, or at least two threads. Ubuntu sees these as two distinct processors and /proc/cpuinfo reflects that.

You can artificially limit this to only pull the first match:

$ grep -m1 "[MG]Hz" /proc/cpuinfo
model name  : Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz

I don't understand the second part of your question. If you want to display that and write it to a file, use tee:

$ grep -m1 "[MG]Hz" /proc/cpuinfo | tee testfile
model name  : Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz

$ cat testfile 
model name  : Intel(R) Core(TM) i7 CPU         920  @ 2.67GHz

If you just want to write it to a file, just redirect it with >. Grep outputs matches to STDOUT, so that will redirect just fine.