This special field allows to set a sorting criteria for the records contained in a record set. Its usage is:
Meaning that the desired order for the records will be determined by
the contents of the fields named
field_name. The sorting is
always done in ascending order, and there may be records not featuring
field_name, i.e. it is not mandatory for the
sorting field to be mandatory :D.
It is an error to have more than one
%sort field in the same
record descriptor, as only one field can be used as sorting criteria.
Consider for example that we want to keep the records in our stockage system ordered by entry date. We could achieve that by using the following record descriptor in the database:
%rec: Item %type: Date date %sort: Date Id: 1 Title: Staplers Date: 10 February 2011 Id: 2 Title: Ruler Pack 20 Date: 2 March 2009 ...
As you can see in the example above, the fact we use
%sort in a
database does not mean that the database will be always physically
ordered. Unsorted record sets are not considered a data integrity
problem, and thus the diagnosis tools must not declare a recfile as
invalid because of this. Some tool may provide a way to physically
order the fields in the file. That is certainly the case of the GNU
recutils, where recfix can be used for that purpose.
On the other hand any program listing, presenting or processing data
extracted from the recfile must honour the
%sort entry. For
example, when using the following recsel program in the
database above we would get the output sorted by date:
$ recsel stockage.rec Id: 2 Title: Ruler Pack 20 Date: 2 March 2009 Id: 1 Title: Staplers Date: 10 February 2011
The sorting of the selected field depends on its type: