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find the intersection of 4 files

How do you find intersection of 4 files?

I used grep -Fx -f 1.txt 2.txt 3.txt 4.txt, but it seems that it only works for 2 files. Similarly comm -12 1.txt 2.txt can't be expanded to 4 files and requires data to be sorted. My data isn't sorted, in fact, it shouldn't be. I am on Mac.

Input:

1.txt
.css
.haha
.hehe
2.txt
.ajkad
.shdja
.hehe

3.txt
.css1
.aaaaa
.hehe

4.txt
.qwqw
.kkkmsm
.hehe

Output: .hehe

I used grep first on 1 and 2 stored in 12.txt, than on 3 and 4,stored in 34.txt then used grep again on 12.txt and 34.txt. But there must be a better way of doing this.

Solution

  • You can chain the greps:

    grep -f 1.txt 2.txt \
| grep -f- 3.txt \
| grep -f- 4.txt

    The -f- means the input coming from the pipe is used, not a real file.