The man manual of comm cannot understand what it meant ..

Comm-compare two sorted files line by line

With no options, produce three-column output. Column one contains lines unique to file1, column two contains lines unique to file2, and column three contains lines common to both files.

 

-1 suppress lines unique to file1

 

-2 suppress lines unique to file2

 

-3 suppress lines that appear in both files

 

I did not understand the problem after I tried the instance for a long time. The translation of these sentences was as follows:

-1 do not display the first column (rows in file1 ).

-2 do not display the second column (rows in file2 ).

-3 do not display the third column (lines public to file1 and file2 ).

 

The three sentences are too BT... It doesn't mean anything at all .. It turns out to be disabled.