Chapter 13. Introduction to the Deploying into Apache Karaf user guide

We already saw the usage of the help command to display all commands available.

But you can also use the help command to get details about a command or the man command which is an alias to the help command. You can also use another form to get the command help, by using the --help option to the command.

So these commands

karaf@root()> help feature:list
karaf@root()> man feature:list
karaf@root()> feature:list --help

All produce the same help output:

DESCRIPTION
        feature:list

        Lists all existing features available from the defined repositories.

SYNTAX
        feature:list [options]

OPTIONS
        --help
                Display this help message
        -o, --ordered
                Display a list using alphabetical order
        -i, --installed
                Display a list of all installed features only
        --no-format
                Disable table rendered output

When you type the tab key, Karaf tries to complete:

An alias is another name associated to a given command.

The shell:alias command creates a new alias. For instance, to create the list-installed-features alias to the actual feature:list -i command, you can do:

karaf@root()> alias "list-features-installed = { feature:list -i }"
karaf@root()> list-features-installed
Name       | Version | Required | State   | Repository     | Description
------------------------------------------------------------------------------------------------------------------------------
feature    | 4.0.0   | x        | Started | standard-4.0.0 | Features Support
shell      | 4.0.0   | x        | Started | standard-4.0.0 | Karaf Shell
deployer   | 4.0.0   | x        | Started | standard-4.0.0 | Karaf Deployer
bundle     | 4.0.0   | x        | Started | standard-4.0.0 | Provide Bundle support
config     | 4.0.0   | x        | Started | standard-4.0.0 | Provide OSGi ConfigAdmin support
diagnostic | 4.0.0   | x        | Started | standard-4.0.0 | Provide Diagnostic support
instance   | 4.0.0   | x        | Started | standard-4.0.0 | Provide Instance support
jaas       | 4.0.0   | x        | Started | standard-4.0.0 | Provide JAAS support
log        | 4.0.0   | x        | Started | standard-4.0.0 | Provide Log support
package    | 4.0.0   | x        | Started | standard-4.0.0 | Package commands and mbeans
service    | 4.0.0   | x        | Started | standard-4.0.0 | Provide Service support
system     | 4.0.0   | x        | Started | standard-4.0.0 | Provide System support
kar        | 4.0.0   | x        | Started | standard-4.0.0 | Provide KAR (KARaf archive) support
ssh        | 4.0.0   | x        | Started | standard-4.0.0 | Provide a SSHd server on Karaf
management | 4.0.0   | x        | Started | standard-4.0.0 | Provide a JMX MBeanServer and a set of MBeans in

At login, the Apache Karaf console reads the etc/shell.init.script file where you can create your aliases. It’s similar to a bashrc or profile file on Unix.

ld = { log:display $args } ;
lde = { log:exception-display $args } ;
la = { bundle:list -t 0 $args } ;
ls = { service:list $args } ;
cl = { config:list "(service.pid=$args)" } ;
halt = { system:shutdown -h -f $args } ;
help = { *:help $args | more } ;
man = { help $args } ;
log:list = { log:get ALL } ;

You can see here the aliases available by default:

You can create your own aliases in the etc/shell.init.script file.

Like on most Unix environment, Karaf console support some key bindings:

You can pipe the output of one command as input to another one. It’s a pipe, using the | character:

karaf@root()> feature:list |grep -i war
pax-war                       | 4.1.4                            |          | Uninstalled | org.ops4j.pax.web-4.1.4  | Provide support of a full WebContainer
pax-war-tomcat                | 4.1.4                            |          | Uninstalled | org.ops4j.pax.web-4.1.4  |
war                           | 4.0.0                            |          | Uninstalled | standard-4.0.0           | Turn Karaf as a full WebContainer
blueprint-web                 | 4.0.0                            |          | Uninstalled | standard-4.0.0           | Provides an OSGI-aware Servlet ContextListener fo

Karaf console provides some core commands similar to Unix environment:

You don’t have to use the fully qualified name of the command, you can directly use the command name as long as it is unique. So you can use 'head' instead of 'shell:head'

Again, you can find details and all options of these commands using help command or --help option.

The Apache Karaf Console supports a complete scripting language, similar to bash or csh on Unix.

The each (shell:each) command can iterate in a list:

karaf@root()> list = [1 2 3]; each ($list) { echo $it }
1
2
3

karaf@root()> a = 0 ; while { %((a+=1) <= 3) } { echo $a }
1
2
3

You can create the list yourself (as in the previous example), or some commands can return a list too.

We can note that the console created a "session" variable with the name list that you can access with $list.

The $it variable is an implicit one corresponding to the current object (here the current iterated value from the list).

When you create a list with [], Apache Karaf console creates a Java ArrayList. It means that you can use methods available in the ArrayList objects (like get or size for instance):

karaf@root()> list = ["Hello" world]; echo ($list get 0) ($list get 1)
Hello world

We can note here that calling a method on an object is directly using (object method argument). Here ($list get 0) means $list.get(0) where $list is the ArrayList.

The class notation will display details about the object:

karaf@root()> $list class
...
ProtectionDomain     ProtectionDomain  null
 null
 <no principals>
 java.security.Permissions@6521c24e (
 ("java.security.AllPermission" "<all permissions>" "<all actions>")
)


Signers              null
SimpleName           ArrayList
TypeParameters       [E]

You can "cast" a variable to a given type.

karaf@root()> ("hello world" toCharArray)
[h, e, l, l, o,  , w, o, r, l, d]

If it fails, you will see the casting exception:

karaf@root()> ("hello world" toCharArray)[0]
Error executing command: [C cannot be cast to [Ljava.lang.Object;

You can "call" a script using the shell:source command:

karaf@root> shell:source script.txt
True!

where script.txt contains:

foo = "foo"
if { $foo equals "foo" } {
  echo "True!"
}

if{ $foo equals "foo" } ...

karaf@root> shell:source script.txt
Error executing command: Cannot coerce echo "true!"() to any of []

As for the aliases, you can create init scripts in the etc/shell.init.script file. You can also named you script with an alias. Actually, the aliases are just scripts.

See the Scripting section of the developers guide for details.