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Compare two files, then overwrite first file with only that in both files

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# 1  
Old 01-16-2013
Compare two files, then overwrite first file with only that in both files
I want to compare two files, and search for items that are in both. Then override the first file with that containing only elements which were in both files. I imagine something with diff, but not sure.

File 1
Code:
One
Two
Three
Four
Five

File 2
Code:
One
Three
Four
Six
Eight

Output (the new File 1)
Code:
One
Three
Four

# 2  
Old 01-16-2013
finding the common items can be done using two ways

Code:
fgrep -f file1 file2

or

Code:
awk 'NR==FNR{a[$1]=$1;next} a[$1]' file1 file2

# 3  
Old 01-16-2013
Code:
Join

should be helpful for you!
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