Add possibility to read password from stdin

VmBackup.py

@@ -65,7 +65,7 @@
 # Usage w/ config file for multiple vm backups, where you can specify either vm-export or vdi-export:
 #    ./VmBackup.py <password> <config-file-path>
 
-import sys, time, os, datetime, subprocess, re, shutil, XenAPI, smtplib, re, base64, socket
+import sys, time, os, datetime, subprocess, re, shutil, XenAPI, smtplib, re, base64, socket, signal
 from email.MIMEText import MIMEText
 from subprocess import PIPE
 from subprocess import STDOUT
@@ -1369,6 +1369,46 @@ def usage_examples():
     print '  ./VmBackup.py /root/VmBackup.pass monthly.cfg'
     print
 
+def read_char_non_block(file_object,Block=True):
+  timeout=1
+  signal.signal(signal.SIGALRM, input)
+  signal.alarm(timeout)
+  try:
+    if Block or select.select([file_object], [], [], 0) == ([file_object], [], []):
+      return file_object.read(1)
+  except:
+      return
+
+def read_password_from_stdin():
+  password=""
+  while True:
+    char = read_char_non_block(sys.stdin)
+    if char:
+       password += char
+    else:
+	if len(password) > 0:
+	  return password.rstrip()
+	else:
+          return
+
+def get_password(password_arg):
+
+    # read password from stdin if password_arg is a dash("-")
+    if password_arg == "-":
+	password = read_password_from_stdin()
+        if password:
+          return password
+        else:
+          raise "FATAL: Could not get password from stdin"
+
+    # return base64-decoded file content if password_arg is an existing file
+    if (os.path.exists(password)): 
+      password = base64.b64decode(open(password, 'r').read())
+      return password
+
+    # else take the given password_arg as clear text password
+    return pasword_arg
+
 if __name__ == '__main__':
     if 'help' in sys.argv or 'config' in sys.argv or 'example' in sys.argv:
         if 'help' in sys.argv: usage_help() 
@@ -1378,11 +1418,9 @@ def usage_examples():
     if len(sys.argv) < 3:
         usage()
         sys.exit(1)
-    password = sys.argv[1]
+    password = get_password(sys.argv[1])
     cfg_file = sys.argv[2]
     # obscure password support
-    if (os.path.exists(password)): 
-        password = base64.b64decode(open(password, 'r').read())
     if cfg_file.lower().startswith('create-password-file'):
         array = sys.argv[2].strip().split('=')
         open(array[1], 'w').write(base64.b64encode(password))