The csv package is a dead-simple Comma Separated Values parser for Common Lisp. It is fast, customizable, and works on streams.
Since there are so many versions of the CSV file, the first thing to do is define the csv-format you'd like to use with make-csv-format:
CL-USER > (make-csv-format :separator '(#\tab))
#S(CSV::CSV-FORMAT :COMMENT #\# :SEPARATOR (#\Tab) :QUOTE #\" :ESCAPE #\\)
Now, it's possible to use that format with one of the read/write CSV functions available.
Read functions:
(read-csv stream &optional format)
(read-record stream &optional format)
Write functions:
(write-csv records stream &optional format)
(write-record record stream &optional format)
There is a global, dynamic format *csv-format* that is used if a format is not provided (which can obviously be overridden lexically).
Parsing a single record:
CL-USER > (with-input-from-string (s "1,2,\"Hello, world!\",NA")
(read-record s))
("1" "2" "Hello, world!" "NA")
Writing a single record:
CL-USER > (write-record * *standard-output*)
1,2,"Hello, world!",NA
That's it!