问题
Can someone please tell me how does sed -n '1!p work ? Below is the full command which I am using to sort my pods in k8s based on nodes they are assigned.
kubectl get pods -o wide --all-namespaces|sort -k8 -r| sed -n '1!p'
The above command works perfectly and the sed part removes the first header line from the final output.
I want to understand how does the sed part work and what's the significance of the parameters passed to sed?
回答1:
From info sed:
-n:
By default, 'sed' prints out the pattern space at the end of each
cycle through the script (*note How 'sed' works: Execution Cycle.).
These options disable this automatic printing, and 'sed' only
produces output when explicitly told to via the 'p' command.
1p: print first line
1!p: do not print first line.
回答2:
By default, sed will output every line it parses.-n option is there to hide this output, and display only the lines specified with the p option.
In your exemple, sed -n '1!p' means "Display every line but first".
A more understandable example is when you want to search/replace with sed. If you want to see the whole resulting file you'll use this:
sed 's/from/to/g' file.txt
But if you only want to see which lines have been changed, use this:
sed -n 's/from/to/gp' file.txt
来源：https://stackoverflow.com/questions/58779782/what-is-the-significance-of-n-parameter-passed-to-sed-command