It's easy if the fields are all numbers and you have a good handle on whether any of them will be negative, in scientific notation, etc.

Once strings are in play, it quickly gets very hairy though, with quoting and escaping that's all over the place.

Badly formed, damaged, or truncated files are another caution area— are you allowed to bail, or required to? Is it up to your parser to flag when something looks hinky so a human can check it out? Or to make a judgment call about how hinky is hinky enough that the whole process needs to abort?