As was explained in the previous sections, recsel outputs
all the records of some record set. The records are echoed in the
same order they are written in the recfile. However, often it is
desirable to select a subset of the records, determined by the position
they occupy in their record set.
The -n command line option to recsel supports doing
this in a natural way. This is how we would retrieve the first
contact listed in a contacts database using recsel:
$ recsel -n 0 contacts.rec Name: Granny Phone: +12 23456677
Note that the index is zero-based. If we want to retrieve more
records we can specify several indexes to -n separated by
commas. If a given index is too big, it is simply ignored:
$ recsel -n 0,1,999 contacts.rec Name: Granny Phone: +12 23456677 Name: Doctor Phone: +12 58999222
With -n, the order in which the records are echoed does not
depend on the order of the indexes passed to -n.
For example, the output of recsel -n 0,1 will be
identical to the output of recsel -n 1,0.
Ranges of indexes can also be used to select a subset of the records. For example, the following call would also select the first three contacts of the database:
$ recsel -n 0-2 contacts.rec Name: Granny Phone: +12 23456677 Name: Doctor Phone: +12 58999222 Name: Dad Phone: +12 88229900
It is possible to mix single indexes and index
ranges in the same call. For example, recsel -n 0,5-6 would
select the first, sixth and seventh records.