bash - Find the similarities between two files

Question

I have two file like:

1
2
3
4
5
6
7
8
9
10

and a file with two columns

1 0.11
2 0.12748
5 0.45
12 0.48
7 0.48
8 0.7
13 0.78
14 0.88

I would like to find thesimilarities between the two files. If the in both files the number in file 1 apper also in the first column of file 2 then it means that there it must appear in the output file. The output should be:

1 0.11
2 0.12748
5 0.45
7 0.48
8 0.7

I tried with different combination of grep but it does not work.

Answer 1

You can use grep -f patt_file file to get the patterns from a file. That is, search in file patterns included in patt_file.

See the output with your given input:

$ grep -w -f file1 file2
1 0.11
2 0.12748
5 0.45
7 0.48
8 0.7

From man grep:

-f FILE, --file=FILE

Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing.