The (somewhat limited) value of 'ccontrol default'

If you have ever issued the command ccontrol help to discover what ccontrol is capable of, perhaps you noticed this section:

Syntax:
        ccontrol default
Description:
        Display the name of the default Cache instance,
        if one has been designated.

Syntax:
        ccontrol default <instance name>
Description:
        Designate the default Cache instance.
Example:
        ccontrol default mystuff

Syntax:
        ccontrol default ""
Description:
        A default instance is not assigned.

But what does it mean to be "the default Cache instance"? My searches of documentation drew a blank.

It turns out to govern the cache command, a shorthand form of the csession <instance name> command, which in turn is a shorthand form of ccontrol session <instance name>

Here's the fruit of my investigation on a test server with five instances. They're actually Ensemble ones, but that doesn't matter.

[root@tra ~]# ccontrol list

Configuration 'DEV'   (default)
        directory: /demo/ensemble/DEV
        versionid: 2012.2.5.962.2
        conf file: cache.cpf  (SuperServer port = 1972, WebServer = 57772)
        status:    down, last used Thu Mar 15 01:30:07 2018

Configuration 'HOM'
        directory: /demo/ensemble/HOM
        versionid: 2012.2.5.962.2
        conf file: cache.cpf  (SuperServer port = 56773, WebServer = 57773)
        status:    down, last used Thu Mar 15 03:35:31 2018

Configuration 'PERSONAL1'
        directory: /demo/ensemble/PERSONAL1
        versionid: 2012.2.5.962.2
        conf file: cache.cpf  (SuperServer port = 56775, WebServer = 57775)
        status:    down, last used Thu Mar 15 03:35:08 2018

Configuration 'PERSONAL2'
        directory: /demo/ensemble/PERSONAL2
        versionid: 2012.2.5.962.2
        conf file: cache.cpf  (SuperServer port = 56776, WebServer = 57776)
        status:    down, last used Thu Mar 15 03:35:08 2018

Configuration 'PROD'
        directory: /demo/ensemble/PROD
        versionid: 2012.2.5.962.2
        conf file: cache.cpf  (SuperServer port = 56774, WebServer = 57774)
        status:    down, last used Thu Mar 15 03:35:06 2018
[root@tra ~]#

Let's see which is the default instance:
[root@tra ~]# ccontrol default
DEV
[root@tra ~]#

This means that I can use the cache command. You'll have to take my word that this would have connected me to the DEV instance. My instances aren't running because their temporary license keys have expired:

[root@tra ~]# cache
Instance is not running
[root@tra ~]#

By clearing the default we eliminate the cache command:

[root@tra ~]# ccontrol default ""
[root@tra ~]# cache
-bash: /usr/bin/cache: No such file or directory
[root@tra ~]#

Setting a default again reinstates the command:

[root@tra ~]# ccontrol default DEV
[root@tra ~]# cache
Instance is not running
[root@tra ~]#

What implements the command?

[root@tra ~]# which cache
/usr/bin/cache
[root@tra ~]# ls -l /usr/bin/cache
lrwxrwxrwx. 1 root root 32 May  3 12:34 /usr/bin/cache -> /usr/local/etc/cachesys/csession
[root@tra ~]# ls -l /usr/local/etc/cachesys/csession
-r-xr-xr-x. 1 cache-dev cacheusr 24325 Dec  1 13:26 /usr/local/etc/cachesys/csession
[root@tra ~]#

I sometimes wish the default instance had meaning on the other ccontrol commands. For example, wouldn't it be handy to be able to issue ccontrol stop without also having to enter an instance name? Particularly if you only have one instance on the server, or if you are trying to create scripts for use on environments where the actual instance name may vary.

Given that command such as ccontrol stop accept optional qualifiers, e.g.

ccontrol stop DEV quietly restart

it would probably be necessary to have a placeholder symbol to represent "default instance". How about this format?

ccontrol stop . quietly restart