Matching two files with awk codes

There are two files

first.file

• M1
• M2
• M3

...

second.file

• A1 M1
• A2 M1
• A2 M3
• A3 M2
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• A3 M4
• A3 M5

....

I want to match first.file to second.file My result file should be like that:

result.file

• A1 M1
• A2 M1
• A2 M3
• A3 M2

How can I do that with awk codes ?

Thank you in advance

awk '
  BEGIN { while (getline < "first.file") { file1[$0]=1 } }
  $2 in file1 { print }
' <second.file

Use the below:

grep -f firstfile secondfile

grep is enough. even though we can do this with awk too,i prefer grep

If you still insist on awk,Then i have a very simple solution in awk too.

awk 'FNR==NR{a[$0];next}($0 in a)' file2 file1

Explanation:

Put file2 entries into an array. Then iterate file1, each time finding those entries in the array.