Merge 2 csv files using powershell append - powershell

Question

I have a csv file called newuser.csv that is generated daily and it's written on top of the old csv file, I created a separate csv called newuser2.csv that I could use to update only the new data from the newuser.csv file.
Here is an example
newuser.csv contains
givenName sn description title
Angel test US Empliyee IT Support Contractor
James test US Empliyee IT Support Contractor
John test US Empliyee IT Support Contractor
newuser2.csv contains
givenName sn description title
Angel test US Empliyee IT Support Contractor
newuser.csv over-written every day
newuser2.csv I created and I would like to pick up changes from the newuser.csv and update and enter those changes to newuser2.csv append.
I tried
#(Import-Csv C:\scripts\test\newusers.csv) + #(Import-Csv C:\scripts\test\newusers2.csv) | Export-Csv C:\scripts\test\newusers2.csv -Append
This did not work as it duplicates the data each time I run the script.
I would really applicate any help as this would save me so much time.

Answer 1

I think the gentle point #MathiasR.Jessen is making, is that we think you are using the wrong word :-). There is different ways to combine data, Overwriting is the -Force parameter e.g.
File1
A
B
File2
C
File1 Overwriting File 2
A
B
Append is "adding to the end" e.g.
File1
A
B
File2
C
File1 Appended to File 2
A
B
C
The word I believe you actually mean is Update. e.g. I want to update the list of users from file1 with the changes in file2. There is no "easy" parameter to do this because it's a more complicated process. For example, you have to choose your "unique identifier" as in, what uniquely identifies the user in order for you to update the right row. Typically this is something like usernames. In this case, without usernames, you can't simply use givenName as your only unique identifier because there may be multiple people with the name "John". Instead you have to (at the very least) see if the user matches by givenName and sn. (EDIT: Can use employeeID as unique identifier)
In this case, I read in the users, updated lists, and loop through both to find users who are in both lists and update the user information. I then export the list.
#Master list
$Users = Import-Csv C:\scripts\test\users.csv
#Update list
$NewUsers = Import-Csv C:\scripts\test\newusers.csv
#Loop through each user and make changes
foreach($User in $Users){
#Loop through new users
foreach($NewUser in $NewUsers){
#See if the user matches by employeeID
if($User.employeeID -eq $NewUser.employeeID)){
#Update User information
$User.description = $NewUser.description
$User.title = $NewUser.title
}
}
}
#Export the updated list
$Users | Export-Csv C:\scripts\test\updatedUsers.csv -Force