> The documentation tells that Fscanln() is similar to Fscan(), my test shows that it isn't true for some cases.
"similar" does not mean "the same as". Fscanln chomps the fields given, then chomps the next character. If the next character is newline, it's happy. If the next character is not a newline, then it's unhappy and returns an error. At this point, you know the input was bad. No guarantees are made about the state of the input after an error, and as you've found, the next character (which *should* have been a newline) has been chomped. On Tuesday, 28 January 2025 at 10:07:28 UTC Ivan Burak wrote: > Hi Howard > > Thank you for the answer. > > My data is easier, it contains only 2 lines: > Go version go1.22.11 windows/amd64 > Build simple, secure, scalable systems with Go > > I did some tests and to speedup coding decided to use Fscanln(). > I don't use this function in real programming, it's too slow. > There are many ways to parse texts in Golang that fast and stable. > > My test algorithm didn't work, and when I realized what the reason was, I > was just surprised. > The documentation tells that Fscanln() is similar to Fscan(), my test > shows that it isn't true for some cases. > In my opinion the documentation or the function should be corrected. > That's it. :) > > >> fmt.Fscanln(in2,&one,&two,&three,&four) > That works but you know in our profession, usually we don't know the exact > amount of data being processed > (number of tokens, records, data volumes etc.), so we have to code based > on estimates n, n^2, n^3 ... and we don't know the real n. > > thanks > ivan > > On Monday, January 27, 2025 at 11:29:32 PM UTC+3 Howard C. Shaw III wrote: > >> In your example, you are repeatedly reading one 'item' from the line. >> This is the source of the confusion, as this is not how Fscanln works - >> when you do this, *each* item is the documented 'final item' after which >> there must be a newline. >> >> That is, your data would look more like this: >> space separated column headers >> first second third last >> some data with the >> same pattern of columns >> >> and your read would be pulling all of those items from one line: >> fmt.Fscanln(in2,&one,&two,&three,&four) >> >> It is expected/designed to read one line of data at a time, and for you >> to know in advance the number of items in the line, and to expect to >> receive an error if they don't match. It is also expected that each column >> will have a consistent datatype, and for that to match the types of your >> parameters, and to error if the data can't be parsed. >> >> For parsing arbitrary string data, you might be better off just using >> bufio.Scanner with bufio.ScanWords. >> > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/3532a16f-824a-4d5d-a5aa-033b46688034n%40googlegroups.com.
