How to convert char[] to int with fail\success control?

Question

this is more like C question, but i failed to google this.

i expect a command parameter in char[], but there may be no argument passed at all, so i need to try to parse this char[] to int and if there is garbage instead of a number, notify user.

i also need to be able to parse negative (with -sign char) numbers from char[].

how can i do this? thanks.

• Mikael Patel: Try atmel.com/webdoc/AVRLibcReferenceManual/…
• Mikael Patel: Alternatively atmel.com/webdoc/AVRLibcReferenceManual/… that will allow fail\success control.
• Mikael Patel: Easiest is maybe atmel.com/webdoc/AVRLibcReferenceManual/… then you can check that 1) a number was parsed, 2) if there are any extra characters, etc.

Answer 1

It isn't doable, reliably, with the given specs. If the array has garbage in it, it won't necessarily fail to parse as an int. That said, you can try to parse as an int with atoi() or sscanf(), as suggested in the comments, and report that it did or did not parse, but not necessarily whether it is valid in some respect.

If you're in control of the array, zero its first element. Then if you get back a non-empty string, at least you'll know some command parameter had been placed in it.

• curly brace: but sscanf did nice job, returning 0 if it can't fill the int variable, thus telling that there is no valid int argument passed.