def _GetProcStatusField(pstatus, field):
  """Retrieves a field from the contents of a proc status file.

  @type pstatus: string
  @param pstatus: Contents of /proc/$pid/status
  @type field: string
  @param field: Name of field whose value should be returned
  @rtype: string

  """
  for line in pstatus.splitlines():
    parts = line.split(":", 1)

    if len(parts) < 2 or parts[0] != field:
      continue

    return parts[1].strip()

  return None