2 added 342 characters in body; edited tags
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$ grep home american.txt | sort | uniq                                                                                            
A home and a country should leave us no more!                                                                                        
Between their loved home and the war's desolation!                                                                                 
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave?     

Why is this showing two duplicate lines?  

Here's the output of grep home american.txt | cat -A:

O'er the land of the free and the home of the brave?^M$
O'er the land of the free and the home of the brave!^M$
A home and a country should leave us no more! ^M$
O'er the land of the free and the home of the brave!^M$
Between their loved home and the war's desolation!^M$
O'er the land of the free and the home of the brave!$
$ grep home american.txt | sort | uniq                                                                                            
A home and a country should leave us no more!                                                                                        
Between their loved home and the war's desolation!                                                                                 
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave?     

Why is this showing two duplicate lines?  

$ grep home american.txt | sort | uniq                                                                                            
A home and a country should leave us no more!                                                                                        
Between their loved home and the war's desolation!                                                                                 
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave?     

Why is this showing two duplicate lines?

Here's the output of grep home american.txt | cat -A:

O'er the land of the free and the home of the brave?^M$
O'er the land of the free and the home of the brave!^M$
A home and a country should leave us no more! ^M$
O'er the land of the free and the home of the brave!^M$
Between their loved home and the war's desolation!^M$
O'er the land of the free and the home of the brave!$
1
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uniq showing duplicate lines

$ grep home american.txt | sort | uniq                                                                                            
A home and a country should leave us no more!                                                                                        
Between their loved home and the war's desolation!                                                                                 
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave!                                                                                  
O'er the land of the free and the home of the brave?     

Why is this showing two duplicate lines?