How do I find common lines in two files

Question

Let's say I have:

text.txt with

1
2
3
4
5

and another text2.txt with

9
4
2
1
7

And I want to extract the duplicates:

2
1
4

Note: I'm using windows, I want it to be as easy as possible

Answer 1

I want to extract the duplicates

Use the following command line:

Findstr /i /x /g:text.txt text1.txt

Where:

• /I Case-insensitive search
• /X Prints lines that match exactly.
• /G:StringsFile Get search string from a file

Source: Findstr - Search for strings - Windows CMD - SS64.com

Example:

F:\test>type text.txt
1
2
3
4
5
F:\test>type text1.txt
9
4
2
1
7
F:\test>Findstr /ixg:text.txt text1.txt
4
2
1
F:\test>Findstr /ixg:text1.txt text.txt
1
2
4

Note that there is no easy way to get the output in the order specified in the question:

2
1
4

as neither of the files contain the lines in that order.

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Further Reading

• An A-Z Index of the Windows CMD command line | SS64.com
• Windows CMD Commands (categorized) - Windows CMD - SS64.com
• Findstr - Search for strings - Windows CMD - SS64.com

Answer 2

With a Unix environment (cygwin on Windows), I would first sort both files (sort text.txt > text.txt.sorted, idem for the second file), then use comm -12 text.txt.sorted text2.txt.sorted