±usenull, ±u

Description

CSV generally does not support a "null" value. It only recognizes empty text fields with a length of 0. These may or may not be enclosed in ±quotechar characters. It makes no difference.

In practice, however, there are applications that distinguish between "empty" fields and "null" fields in their CSV import files.
Null fields are defined as having no value at all, not simply an empty text field.

If you use such an application, there is already an informal convention for it at CSV: while each "empty" text field with a length of 0 consists of two consecutive ±quotechar characters between the delimiters, "null" fields are not present and are not enclosed; they are only identified by two consecutive delimiters.

The default value for ±usenull is "no", i.e. this setting is disabled.

pattern

[source example for the difference is still missing]

function

Setting ±usenull=yes changes a few more things:
All newly created empty fields (with ±add without content) will be null instead of leer.
±clear means that the field(s) will be displayed instead of leer. null instead of empty.

Examples of use

csvfox infile.csv +d=";" +u (...)

Assumes that the file to be read, CSV, has a semicolon as the field delimiter and differentiates between ...;"";... (empty) and ...;;... (null) as above.

csvfox infile.csv -u outfile.csv

Reads infile.csv (without usenull mode) and writes them to outfile.csv, using usenull mode. However, since no null fields were recognized in the input file, the only effect is that empty fields, which were not enclosed in double quotes in the input file, are now enclosed in double quotes in the output file.

csvfox infile.csv +d=";" -d=pipe outfile.csv

[To replace] Reads infile.csv with the given field delimiter ";" and writes it to outfile.csv, using a pipe character ("|") as the field delimiter when writing.
infile.csv:

Spring;Summer;Autumn;Winter blossoms;"green leaves";"fruits and nuts";"tiles stove" bicycle;cabrio;pick-up;sledge

outfile.csv:

Spring|Summer|Autumn|Winter blossoms|"green leaves"|"fruits and nuts"|"tiles stove" bicycle|cabrio|pick-up|sledge