ETL tools and similar things will generally have a go at this. e.g. the Import Flat File wizard in SQL Server Delimted File metadata tool in Talend Basically

ETL tools and similar things will generally have a go at this. e.g. the Import Flat File wizard in SQL Server Delimted File metadata tool in Talend Basically they look at the first N rows and take a guess. If the guess turns out to be wrong its usually worse than not guessing at all.