Finding common value across multiple files containing single column values

Question

I have 100 text files containing single columns each. The files are like:

file1.txt
10032
19873
18326

file2.txt
10032
19873
11254

file3.txt
15478
10032
112         


        

Answer 1

Files with a single column?

You can sort and compare this files, using shell:

for f in file*.txt; do sort $f|uniq; done|sort|uniq -c -d

Last -c is not necessary, it's need only if you want to count number of occurences.