grep -f file to print in order as a file

Question

I have a a requirement to grep patterns from a file but need them in order.

$ cat patt.grep
name1
name2

$ grep -f patt.grep myfile.log
name2:some xxxxxxxxxx
name1:some xxxxxxxxxx

I am getting the output as name2 was found first it was printed then name1 is found it is also printed. But my requirement is to get the name1 first as per the order of patt.grep file.

I am expecting the output as

name1:some xxxxxxxxxx
name2:some xxxxxxxxxx

Answer 1

You can pipe patt.grep to xargs, which will pass the patterns to grep one at a time.

By default xargs appends arguments at the end of the command. But in this case, grep needs myfile.log to be the last argument. So use the -I{} option to tell xargs to replace {} with the arguments.

cat patt.grep | xargs -Ihello grep hello myfile.log

Answer 2

Use the regexes in patt.grep one after another in order of appearance by reading line-wise:

while read ptn; do grep $ptn myfile.log; done < patt.grep

Answer 3

i tried the same situation and easily solved using below command:

I think if your data in the same format as you represent then you can use this.

grep -f patt.grep myfile.log | sort