A quick method to remove duplicates from text files - including for example CSV files - where multiple records have been added (perhaps automatically) at different times resulting in multiple copies of the same record scattered throughout the file. Here is a simple one-liner bash command to remove duplicates using sort.
This method is sensitive to the line endings of the file. If you have files editing in a combination of Unix/Linux/Mac/Windows you may have a variety of line-endings in place.
The simplest route is to run the file through
dos2unixbefore attempting the sort/unique filter.
In a bash shell enter:
sort -u file.csv -o file.csv
This takes your file, sorts it (using sort), gets the unique entries (-u) and writes it to the outfile (-o) which here is the same as the initial file.