As a French citizen you can be admitted to Canada without a visa as a visitor for either tourism or business. Going to a job interview is an allowed activity. When you show up at the border the officer decides how long you will be allowed to stay, based in part on your reason for bring there. That can be for up to six months but may be shorter.
When you leave Canada and attempt to reenter you have to go through the process again. You explain your reason for being there, and the officer decides how long to admit you for. If you have recently been in Canada it will likely be less than six months. If you do it too frequently or for too much time you may be suspected of trying to live in Canada through repeated visits, in which case you would be denied entry.
Which brings us to your reason for being in Canada. Six months is a long time to spend job hunting, so I have to point out that you cannot work in Canada without a permit, for any length of time at all. You or your employer would need to apply for a work permit once you had found a job. Failing to do that can get you deported and banned. Once you have the work permit a six month limit would not be a problem, nor would reentry.