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|
# # Subexec
# * by Peter Kieltyka
# * http://github/nulayer/subexec
#
# ## Description
#
# Subexec is a simple library that spawns an external command with
# an optional timeout parameter. It relies on Ruby 1.9's Process.spawn
# method. Also, it works with synchronous and asynchronous code.
#
# Useful for libraries that are Ruby wrappers for CLI's. For example,
# resizing images with ImageMagick's mogrify command sometimes stalls
# and never returns control back to the original process. Subexec
# executes mogrify and preempts if it gets lost.
#
# ## Usage
#
# # Print hello
# sub = Subexec.run "echo 'hello' && sleep 3", :timeout => 5
# puts sub.output # returns: hello
# puts sub.exitstatus # returns: 0
#
# # Timeout process after a second
# sub = Subexec.run "echo 'hello' && sleep 3", :timeout => 1
# puts sub.output # returns:
# puts sub.exitstatus # returns:
class Subexec
VERSION = '0.2.3'
attr_accessor :pid,
:command,
:lang,
:output,
:exitstatus,
:timeout,
:log_file
def self.run(command, options={})
sub = new(command, options)
sub.run!
sub
end
def initialize(command, options={})
self.command = command
self.lang = options[:lang] || "C"
self.timeout = options[:timeout] || -1 # default is to never timeout
self.log_file = options[:log_file]
self.exitstatus = 0
end
def run!
if RUBY_VERSION >= '1.9' && RUBY_ENGINE != 'jruby'
spawn
else
exec
end
end
private
def spawn
# TODO: weak implementation for log_file support.
# Ideally, the data would be piped through to both descriptors
r, w = IO.pipe
log_to_file = !log_file.nil?
log_opts = log_to_file ? {[:out, :err] => [log_file, 'a']} : {STDERR=>w, STDOUT=>w}
self.pid = Process.spawn({'LANG' => self.lang}, command, log_opts)
w.close
@timer = Time.now + timeout
timed_out = false
self.output = ''
append_to_output = Proc.new do
self.output << r.readlines.join('') unless log_to_file
end
loop do
ret = begin
Process.waitpid(pid, Process::WUNTRACED|Process::WNOHANG)
rescue Errno::ECHILD
break
end
break if ret == pid
append_to_output.call
if timeout > 0 && Time.now > @timer
timed_out = true
break
end
sleep 0.01
end
if timed_out
# The subprocess timed out -- kill it
Process.kill(9, pid) rescue Errno::ESRCH
self.exitstatus = nil
else
# The subprocess exited on its own
self.exitstatus = $?.exitstatus
append_to_output.call
end
r.close
self
end
def exec
if !(RUBY_PLATFORM =~ /win32|mswin|mingw/).nil?
self.output = `set LANG=#{lang} && #{command} 2>&1`
else
self.output = `LANG=#{lang} && export LANG && #{command} 2>&1`
end
self.exitstatus = $?.exitstatus
end
end
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