Module: Bosh::Exec

Defined in:
lib/common/exec.rb,
lib/common/exec/error.rb,
lib/common/exec/result.rb

Overview

Copyright © 2012 VMware, Inc.

Defined Under Namespace

Classes: Error, Result

Class Method Summary collapse

Class Method Details

.included(base) ⇒ Object

Helper method to add sh as a class method when it is included



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# File 'lib/common/exec.rb', line 83

def self.included(base)
  base.extend(Bosh::Exec)
end

.sh(command, options = {}) {|Bosh::Exec::Result| ... } ⇒ Bosh::Exec::Result

Note:

As commands are executed using %x… you need to append 2>&1 to redirect stderr or it will be output to the stderr of the process invoking the sh method

Execute commands in a way that forces you to deal with failures and helps you to simplify testing. The module can be included which will add sh both as an instance and a class method.

A sample way to mock the execution of “ls /”:

it "should be possible to mock the result of a command execution" do
  cmd = "ls /"
  result = Bosh::Exec::Result.new(cmd, "bin etc var", "", 0)
  Bosh::Exec.should_receive(:sh).with(cmd).and_return(result)
  result = Bosh::Exec.sh(cmd)
  result.success?.should be(true)
end

Examples:

by default execute block only when command succeeds and raise

error on failure
sh("command") do |result|
  ...
end

don’t raise error if the command fails

result = sh("command", :on_error => :return)

execute block only when command fails (which implies

:on_error => :return)
sh("command", :yield => :on_false) do |result|
  ...
end

Parameters:

  • command (String) —

    shell command to execute

  • options (Hash) (defaults to: {})

Options Hash (options):

  • :on_error (Symbol) —

    if set to :return failing commands return [Bosh::Exec::Result] instead of raising [Bosh::Exec::Error]

  • :yield (Symbol) —

    if set to :on_false it will execute the block when the command fails, else it will execute the block only when the command succeeds. Implies :on_error = :return

Yields:

Returns:

Raises:

  • (Bosh::Exec::Error) —

    raised when the command isn’t found or the command exits with a non zero status



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# File 'lib/common/exec.rb', line 52

def sh(command, options={})
  opts = options.dup
  # can only yield if we don't raise errors
  opts[:on_error] = :return if opts[:yield] == :on_false

  output = %x{#{command}}
  result = Result.new(command, output, $?.exitstatus)

  if result.failed?
    unless opts[:on_error] == :return
      raise Error.new(result.exit_status, command, output)
    end
    yield result if block_given? && opts[:yield] == :on_false

  else
    yield result if block_given?
  end

  result
rescue Errno::ENOENT => e
  msg = "command not found: #{command}"

  raise Error.new(nil, command) unless opts[:on_error] == :return

  result = Result.new(command, msg, -1, true)

  yield result if block_given? && opts[:yield] == :on_false
  result
end