When/why is it a bad idea to use the fscanf() function?

Question

In an answer there was an interesting statement: "It's almost always a bad idea to use the fscanf() function as it can leave your file pointer in an unknown location on failure. I prefer to use fgets() to get each line in and then sscanf() that."

Could you expand upon when/why it might be better to use fgets() and sscanf() to read some file?

Answer 1

Imagine a file with three lines:

   1
   2b
   c

Using fscanf() to read integers, the first line would read fine but on the second line fscanf() would leave you at the 'b', not sure what to do from there. You would need some mechanism to move past the garbage input to see the third line.

If you do a fgets() and sscanf(), you can guarantee that your file pointer moves a line at a time, which is a little easier to deal with. In general, you should still be looking at the whole string to report any odd characters in it.

I prefer the latter approach myself, although I wouldn't agree with the statement that "it's almost always a bad idea to use fscanf()"... fscanf() is perfectly fine for most things.