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

awk to the rescue!

to find the common element in all files (assuming uniqueness within the same file)

awk '{a[$1]++} END{for(k in a) if(a[k]==ARGC-1) print k}' files

count all occurrences and print the values where count equals number of files.