[#2] - Added basic shell usage class

Basic shell usage class for running bash commands or scripts

Resolves #2

.coveragerc

@@ -3,4 +3,5 @@ omit =
     */python?.?/*
     */site-packages/nose/*
     *__init__*
-	tests/*
+	tests/*
+	env.py

scripts/shell.py

@@ -0,0 +1,46 @@
+import os, subprocess
+
+# The shell class defines just a few functions which can make executing commands easier
+# run
+# 	This command has two possible ways to be called
+# 	(command) which is just a single line with all arguments
+# 	(command, args) which simply just joins a string with the command and arguments
+# 
+# It is also possible to change the current working directory (cwd)
+# for commands which are sensitive to file locations
+# (Unfortunately 'cd' doesn't work)
+
+# If no arguments are passed for args, then it is assumed to be a string of length 0
+# If no arguments are passed to the constructor we assume default cwd
+
+class Shell:
+
+	cwd = ''
+
+	def run(self, command, args=''):
+
+		if len(args) > 0:
+			command = ' '.join([command, args.join(' ')])
+
+		path = os.getcwd()
+		if len(self.cwd) > 0:
+			process = subprocess.Popen(command, shell=True, cwd=path, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
+		else:
+			process = subprocess.Popen(command, shell=True, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
+		output = process.communicate()
+		return output
+
+
+	# set_cwd
+	# equivalent to doing a 'cd' command at the command line
+	# Error if the directory doesn't exist
+	def set_cwd(self, new_cwd):
+		if not os.path.exists(new_cwd):
+			raise IOError(' '.join([self.cwd, 'does not exist']))
+		else:
+			self.cwd = new_cwd
+
+	def __init__(self, wd=''):
+		if not wd == '':
+			self.set_cwd(wd)
+

tests/test_shell.py

@@ -0,0 +1,40 @@
+import unittest
+from env import scripts
+from scripts.shell import Shell
+
+class TestShell(unittest.TestCase):
+	def test_default_cwd(self):
+		try:
+			cmd = Shell()
+		except IOError as e:
+			self.fail('No argument shell constructor should not raise IOError')
+
+	def test_nonexistent_cwd(self):
+		try:
+			cmd = Shell('/missing/directory')
+			self.fail('Should raise IOError on setting nonexistent directory')
+		except IOError as e:
+			return
+
+	def test_existing_directory(self):
+		try:
+			# Actual Directory
+			cmd = Shell('/tmp')
+		except IOError as e:
+			self.fail('Valid path should pass here')
+
+	def test_simple_run(self):
+		try:
+			cmd = Shell('/tmp');
+			out = cmd.run('bash --version')
+			out = cmd.run('bash', '--version')
+		except Exception:
+			self.fail('Exception should not have been raised')
+
+	def test_default_cwd(self):
+		try:
+			cmd = Shell('');
+			out = cmd.run('bash --version')
+			out = cmd.run('bash', '--version')
+		except Exception:
+			self.fail('Exception should not have been raised')