class RVM::Shell::AbstractWrapper

Provides the most common functionality expected of a shell wrapper. Namely, implements general utility methods and tools to extract output from a given command but doesn't actually run any commands itself, leaving that up to concrete implementations.

Usage

Commands are run inside of a shell (usually bash) and can either be exectuted in two situations (each with wrapper methods available) - silently or verbosely.

Silent commands (via run_silently and run_command) do exactly as they say - that can modify the environment etc but anything they print (to stdout or stderr) will be discarded.

Verbose commands will run the command and then print the command epilog (which contains the output stastus and the current env in yaml format). This allows us to not only capture all output but to also return the exit status and environment variables in a way that makes persisted shell sessions possible.

Under the hood, run and run_silently are the preferred ways of invoking commands - if passed a single command, they'll run it as is (much like system in ruby) but when given multiple arguments anything after the first will be escaped (e.g. you can hence pass code etc). run will also parse the results of this epilog into a usable RVM::Shell::Result object.

run_command and run_command_silently do the actual hard work for these behind the scenes, running a string as the shell command. Hence, these two commands are what must be implemented in non-abstract wrappers.

For an example of the shell wrapper functionality in action, see RVM::Environment which delegates most of the work to a shell wrapper.

Constants

COMMAND_EPILOG_END

Used to mark the end of the commands epilog.

COMMAND_EPILOG_START

Used the mark the end of a commands output and the start of the rvm env.

WRAPPER_LOCATION

The location of the shell file with the epilog function definition.

Attributes

shell_executable[R]

Defines the shell exectuable.

Public Class Methods

new(sh = 'bash', &setup_block) click to toggle source

Initializes a new shell wrapper, including setting the default setup block. Implementations must override this method but must ensure that they call super to perform the expected standard setup.

# File lib/rvm/shell/abstract_wrapper.rb, line 52
def initialize(sh = 'bash', &setup_block)
  setup &setup_block
  @shell_executable = sh
end

Public Instance Methods

[](var_name) click to toggle source

Returns a given environment variables' value.

# File lib/rvm/shell/abstract_wrapper.rb, line 96
def [](var_name)
  run(:true)[var_name]
end
run(command, *arguments) click to toggle source

Runs the gives command (with optional arguments), returning an RVM::Shell::Result object, including stdout / stderr streams. Under the hood, uses run_command to actually process it all.

# File lib/rvm/shell/abstract_wrapper.rb, line 69
def run(command, *arguments)
  expanded_command = build_cli_call(command, arguments)
  status, out, err = run_command(expanded_command)
  Result.new(expanded_command, status, out, err)
end
run_command(full_command) click to toggle source

Given a command, it will execute it in the current wrapper and once done, will return:

  • the hash from the epilog output.

  • a string representing stdout.

  • a string representing stderr.

# File lib/rvm/shell/abstract_wrapper.rb, line 86
def run_command(full_command)
  raise NotImplementedError.new("run_command is only available in concrete implementations")
end
run_command_silently(full_command) click to toggle source

Like run_command, but doesn't care about output.

# File lib/rvm/shell/abstract_wrapper.rb, line 91
def run_command_silently(full_command)
  raise NotImplementedError.new("run_command_silently is only available in concrete implementations")
end
run_silently(command, *arguments) click to toggle source

Wrapper around run_command_silently that correctly escapes arguments. Essentially, run but using run_command_silently.

# File lib/rvm/shell/abstract_wrapper.rb, line 77
def run_silently(command, *arguments)
  run_command_silently build_cli_call(command, arguments)
end
setup(&blk) click to toggle source

Defines a setup block to be run when initiating a wrapper session. Usually used for doing things such as sourcing the rvm file. Please note that the wrapper file is automatically source.

The setup block should be automatically run by wrapper implementations.

# File lib/rvm/shell/abstract_wrapper.rb, line 62
def setup(&blk)
  @setup_block = blk
end

Protected Instance Methods

command_complete?(c) click to toggle source

Checks whether the given command includes a epilog, marked by epilog start and end lines.

# File lib/rvm/shell/abstract_wrapper.rb, line 126
def command_complete?(c)
  start_index, end_index = c.index(COMMAND_EPILOG_START), c.index(COMMAND_EPILOG_END)
  start_index && end_index && start_index < end_index
end
invoke_setup!() click to toggle source

When called, will use the current environment to source the wrapper scripts as well as invoking the current setup block. as defined on initialization / via setup.

# File lib/rvm/shell/abstract_wrapper.rb, line 104
def invoke_setup!
  source_command_wrapper
  @setup_block.call(self) if @setup_block
end
raw_stdout_to_parts(c) click to toggle source

Takes a raw string from a processes STDIO and returns three things:

  1. The actual stdout, minus epilogue.

  2. YAML output of the process results.

  3. Any left over from the STDIO text.

# File lib/rvm/shell/abstract_wrapper.rb, line 135
def raw_stdout_to_parts(c)
  raise IncompleteCommandError if !command_complete?(c)
  before, after = c.split(COMMAND_EPILOG_START, 2)
  epilog, after = after.split(COMMAND_EPILOG_END, 2)
  return before, YAML.load(epilog.strip), after
end
silent_command(command) click to toggle source

Wraps a command in a way that it prints no output.

# File lib/rvm/shell/abstract_wrapper.rb, line 120
def silent_command(command)
  "{ #{command}; } >/dev/null 2>&1"
end
source_command_wrapper() click to toggle source

Uses run_silently to source the wrapper file.

# File lib/rvm/shell/abstract_wrapper.rb, line 110
def source_command_wrapper
  run_silently :source, WRAPPER_LOCATION
end
wrapped_command(command) click to toggle source

Returns a command followed by the call to show the epilog.

# File lib/rvm/shell/abstract_wrapper.rb, line 115
def wrapped_command(command)
  "#{command}; __rvm_show_command_epilog"
end