Looking for script to compare entries of new file(File2) in already existed file F1

[tvnaidu]

I am looking for script to compare a new entry from File2 in File1:

I have Two files, once file (File1) contains e-mail ids which are already sorted and another file (File2) contains new e-mail ids received, I want to see if those ids (File2) are already existed in file1. Can I get a shell script or program for that?

File1:
[e-mail]
[e-mail]
xyz3@gmailcom


FILE2:
[e-mail]
[e-mail]

I want to insert all FILe2 entried into File1, if entry exists in File1, then I want to ignore.

[RedSon]

You can use the "diff" command. Type diff --help or man diff.

[tvnaidu]

The first file (FILE1) contains atleast 1500 entries, second file (File2) contains only 100 entries, If I merge second file into first one, I might have duplicate entries, I want to read one one entry from second file (File2) and compare that entry against first file, if that entry doesn't exist, then I wanto to insert that entry intyo first one, like that all entries in second file should get verified, if not there, then insert that entry into first one.

[RedSon]

Then you want to use "diff" and "patch" in your script. First you diff, then you apply that diff on the other file with patch.