JavaScript Console

Ccmchain implements a javascript runtime environment (JSRE) that can be used in either interactive (console) or non-interactive (script) mode.

Ccmchain's Javascript console exposes the full web3 JavaScript Dapp API and the admin API.

Interactive use: the JSRE REPL Console

The ccmchain CLI executable gccm has a JavaScript console (a Read, Evaluate & Print Loop = REPL exposing the JSRE), which can be started with the console or attach subcommand. The console subcommands starts the gccm node and then opens the console. The attach subcommand will not start the gccm node but instead tries to open the console on a running gccm instance.

$ gccm console
$ gccm attach

The attach node accepts an endpoint in case the gccm node is running with a non default ipc endpoint or you would like to connect over the rpc interface.

$ gccm attach ipc:/some/custom/path
$ gccm attach http://191.168.1.1:8545
$ gccm attach ws://191.168.1.1:8546

Note that by default the gccm node doesn't start the http and weboscket service and not all functionality is provided over these interfaces due to security reasons. These defaults can be overridden when the --rpcapi and --wsapi arguments when the gccm node is started, or with admin.startRPC and admin.startWS.

If you need log information, start with:

$ gccm --verbosity 5 console 2>> /tmp/log

Otherwise mute your logs, so that it does not pollute your console:

$ gccm console 2>> /dev/null

or

$ gccm --verbosity 0 console

Gccm has support to load custom JavaScript files into the console through the --preload argument. This can be used to load often used functions, setup web3 contract objects, or ...

gccm --preload "/my/scripts/folder/utils.js,/my/scripts/folder/contracts.js" console

Non-interactive use: JSRE script mode

It's also possible to execute files to the JavaScript interpreter. The console and attach subcommand accept the --exec argument which is a javascript statement.

$ gccm --exec "ccm.blockNumber" attach

This prints the current block number of a running gccm instance.

Or execute a local script with more complex statements on a remote node over http:

$ gccm --exec 'loadScript("/tmp/checkbalances.js")' attach http://123.123.123.123:8545
$ gccm --jspath "/tmp" --exec 'loadScript("checkbalances.js")' attach http://123.123.123.123:8545

Use the --jspath <path/to/my/js/root> to set a libdir for your js scripts. Parameters to loadScript() with no absolute path will be understood relative to this directory.

You can exit the console cleanly by typing exit or simply with CTRL-C.

Caveat

The ccmchain JSRE uses the Otto JS VM which has some limitations:

• "use strict" will parse, but does nothing.
• The regular expression engine (re2/regexp) is not fully compatible with the ECMA5 specification.

Note that the other known limitation of Otto (namely the lack of timers) is taken care of. Ccmchain JSRE implements both setTimeout and setInterval. In addition to this, the console provides admin.sleep(seconds) as well as a "blocktime sleep" method admin.sleepBlocks(number).

Since web3.js uses the bignumber.js library (MIT Expat Licence), it is also autoloded.

Timers

In addition to the full functionality of JS (as per ECMA5), the ccmchain JSRE is augmented with various timers. It implements setInterval, clearInterval, setTimeout, clearTimeout you may be used to using in browser windows. It also provides implementation for admin.sleep(seconds) and a block based timer, admin.sleepBlocks(n) which sleeps till the number of new blocks added is equal to or greater than n, think "wait for n confirmations".

Management APIs

Beside the official DApp API interface the go ccmchain node has support for additional management API's. These API's are offered using JSON-RPC and follow the same conventions as used in the DApp API. The go ccmchain package comes with a console client which has support for all additional API's.

The management API has its own wiki page.