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Juan Cruz Viotti d9822faf2f fix(GUI): emit progress back to parent using node-ipc (#774 )

This PR makes use of `node-ipc` to emit progress information from the
child CLI to the GUI process rather than the tailing approach we've
been doing until now.

This change was motivated by the following Electron fix which landed in
v1.4.4: https://github.com/electron/electron/pull/7578. Before such fix,
Electron would not output anything to stdout/stderr if the Electron
process was running with `ELECTRON_RUN_AS_NODE` under Windows, which
forced us to implement `--log` option in the Etcher CLI to output state
information to a file.

Since this issue is fixed, we can consume the Etcher CLI output from
within `child_process.spawn`, which opens more interesting possibilities
for sharing information between both processes.

This coindentally fixes a Windows issue where the tailing module would
receive malformed JSON, causing Etcher to crash at `JSON.parse`. The
reason of this problem was a bug in the tailing module we were using.

Fixes: https://github.com/resin-io/etcher/issues/642
Change-Type: patch
Changelog-Entry: Fix "Unexpected end of JSON" error in Windows.
Signed-off-by: Juan Cruz Viotti <jviotti@openmailbox.org>

2016-10-25 23:56:39 -04:00

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Etcher CLI

The Etcher CLI is a command-line tool that aims to provide all the benefits of the Etcher desktop application in a way that can be ran from a terminal, or even used from a script.

In fact, the Etcher desktop application is simply a wrapper around the CLI, which the place where the actual writing logic takes place.

Running

We are not oficially releasing the Etcher CLI as a separate package yet, but you can run it locally with the following steps:

Clone the Etcher repository.

git clone https://github.com/resin-io/etcher

Install the dependencies, using the instructions from CONTRIBUTING.md.
Run the Etcher CLI from bin/etcher.

./bin/etcher --help

Options

  --help, -h     show help
  --version, -v  show version number
  --drive, -d    drive
  --check, -c    validate write
  --robot, -r    parse-able output without interactivity
  --yes, -y      confirm non-interactively
  --unmount, -u  unmount on success

The robot option

The --robot option is very particular since it allows other applications to easily consume the output of the Etcher CLI in real-time. When using the --robot option, the --yes option is implicit, therefore you need to manually specify --drive.

When --robot is used, the program will output JSON lines containing the progress state and other useful information. For example:

$ sudo etcher image.iso --robot --drive /dev/disk2
{"command":"progress","data":{"type":"write","percentage":1,"eta":130,"speed":1703936}}
...
{"command":"progress","data":{"type":"check","percentage":100,"eta":0,"speed":17180514}}
{"command":"done","data":{"sourceChecksum":"27c39a5d"}}

The command property can be used to determine the action taking place, while the data property contains extra information related to the command.

Exit codes

The Etcher CLI uses certain exit codes to signal the result of the operation. These are documented in lib/src/exit-codes.js and are also printed on the Etcher CLI help page.

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