I have a client who is given a tab delimited .txt file containing hundreds of thousands of rows.

I have a user story as follows:

As a user I want to take the text file and add a new value at the end of each line which contains the concatenated value of two of the columns.

for example if the file read

text_one    text_two

I need to output the following (preferably to a .txt file)

text_one    text_two    text_onetext_two

My first approach was to ask the vendor supplying the file to do the concatenation before providing the file, the easiest way to solve a problem is to eliminate it right? however they are very uncooperative and have point blank refused.

I've looked at building a simple javascript application that does this client side so a non-technical user could select the file using a file selector. This approach has a few problems

• The file could be over a GB in size and so can't be loaded straight into memory, I've tried and the browser crashes
• There is no means to write a file in javascript so I'd need to output the content to the screen and have the user save it (somehow)

I was thinking if I could get around the filesize limitations I could just output the edited content to the page and have the user save the page as a .txt file, however I think there is a better way than using javascript that will still accommodate the users lack of technical know-how.

Please consider this question to be stack agnostic, but bear in mind that a nice little shell script or python script would be deemed unsuitable for a non technical user unless there is a way of "packaging" it nicely for a non-technical user.

Updates

The file is too large to open in excel. The process needs to be run weekly, but it doesn't require scheduling or automation...(yet)