Scmd

Build and run system commands. Scmd uses posix-spawn to fork child processes to run the commands.

Usage

Create a command object:

cmd = Scmd.new("echo hi")

cmd.to_s    #=> "echo hi"
cmd.inspect #=> #<Scmd::Command:0x83220514 @cmd_str="echo hi" @exitstatus=nil>

cmd.pid        #=> nil
cmd.exitstatus #=> nil
cmd.stdout     #=> ''
cmd.stderr     #=> ''

Run it:

cmd.run

OR, async run it:

cmd.start
cmd.running? # => true
cmd.pid      #=> 12345

# do other stuff...
cmd.wait # indefinitely until cmd exits

OR, async run it with a timeout:

cmd.start

begin
  cmd.wait(10)
rescue Scmd::Timeout => err
  cmd.stop # attempt to stop the cmd nicely, kill if doesn't stop in time
  cmd.kill # just kill the cmd now
end

Results:

# written to the cmd instance
cmd.pid        #=> 12345
cmd.exitstatus #=> 0
cmd.stdout     #=> 'hi'
cmd.stderr     #=> ''

# the cmd instance is returned by `run` for chaining as well
cmd.run.stdout #=> 'hi'

Run with input on stdin

A single input line

input = "echo hi"
cmd = Scmd.new("sh").run(input)
cmd.stdout #=> 'hi'

Multiple input lines:

input = ["echo hi", "echo err 1>&2"]
cmd = Scmd.new("sh").run(input)
cmd.stdout #=> 'hi'
cmd.stderr #=> 'err'

Some helpers

Ask if cmd was successful:

puts cmd.stderr if !cmd.success?

Raise an exception if not successful with run!:

Scmd.new("cd /path/that/does/not/exist").run! #=> Scmd::Command::Failure

Environment variables

Pass environment variables:

cmd = Scmd.new("echo $TEST_VAR", {
  :env => {
    'TEST_VAR' => 'hi'
  }
})

Process spawn options

Pass options:

reader, writer = IO.pipe
# this is an example that uses file descriptor redirection options
cmd = Scmd.new("echo test 1>&#{writer.fileno}", {
  :options => { writer => writer }
})
reader.gets # => "test\n"

For all the possible options see posix-spawn.

Installation

Add this line to your application's Gemfile:

gem 'scmd'

And then execute:

$ bundle

Or install it yourself as:

$ gem install scmd

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request