Each elective and appointive officer shall, before entering upon his duties, take and subscribe to the following oath or affirmation, to be filed and kept in the office of the City Clerk:
   "I solemnly swear (or affirm) that I will support the constitution of the United States of America and of the State of West Virginia, and that I will, in all respects, observe the provisions of the Charter, ordinances, resolutions, regulations and rules of the City of South Charleston, and will faithfully discharge the duties of                               to the best of my skill and judgment."
   When an officer or employee of the City shall have filed such oath with the City Clerk and shall have given bond as required by law, he shall be considered having qualified for the position to which he was elected or appointed; provided, however, that if any person so elected or appointed shall not qualify in the manner herein prescribed within twenty days after he shall have been officially declared elected or appointed thereto, said position shall by reason thereof become vacant.