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how to show lines in common (reverse diff)?
Is there a command to do the opposite of diff? I want to compare two files if the same thing exists in both create a list of them. i am trying to figure out what entry's exist in both files.
Here is a solution that WILL NOT change the order of the lines:
fgrep -x -f file1 file2
Use the join command:
join a.txt b.txt
assuming the files are sorted; if not:
sort a.txt > sorted_a.txt; sort b.txt > sorted_b.txt; join sorted_a.txt sorted_b.txt
来源：https://stackoverflow.com/questions/8581090/how-to-do-the-opposite-of-diff