difference between the content of two files

Question

I have two files one file subset of other and i want to obtain a file which has contents not common to both.for example

File1

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Answer 1

1 Only one instance , in either

• cat File1 File2 | sort | uniq -u

2 Only in first file

• cat File1 File2 File2 | sort | uniq -u

3 Only in second file

• cat File1 File1 File2 | sort | uniq -u