On Thu, 19 Jan 2017 00:05:46 -0800 (PST) hui zhang <fastfad...@gmail.com> wrote:
> check below link > > http://stackoverflow.com/questions/1821811/how-to-read-write-from-to-file-using-golang > > It offer 3 ways. > os > *bufio* > *ioutil* There's just a single way to read a file -- using the Read() method on values of type *os.File. That's because this method function in the end uses an appropriate low-level OS call which reads data from an opened file, and trust me -- the wrapping around such a call implemented in os.File.Read() is very very thin. All the other things you referred to are not "methods to read a file" -- they are *approaches* to do that using a strategy which suits your application best. Several points to understand this: * os.File.Read() is unbuffered: each time you call it, it, in turn, calls into the OS kernel. Calling into kernel is *slow,* so when you just need to read the file's data from start to end in chunks of some size (or varying sizes), the best strategy is to use buffering -- that is, on each read round, to read as much as possible (available) so that the next read operation will be served from a buffer and no call to the OS will be made. OK, so there's bufio.Reader for this. * os.File.Read() is free to read less data than you asked it for. That is, you can pass it a slice of length 4000, but it's free to return just a single byte. That's not Go -- that's how OSes work. So if you need to read exactly 4000 bytes, you can certainly roll your own looping logic, but io.ReadFull() exists for exactly this purpose. TL;DR Any "non-standard method to read a file" you may encounter in the standard library is -- in the end -- just a wrapper around the io.Reader interface implemented by values of type *os.File. They provide various convenient ways to access the file using the best pattern for the task at hand. -- 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. For more options, visit https://groups.google.com/d/optout.
