We're making a log processing program that needs to parse times from the prefix of a larger string, in this case in a log line such as:
2006-01-02 15:04:05 INFO this is a log message We need to parse the "2006-01-02 15:04:05" part as a timestamp. Unfortunately, time.Parse always returns an error if there's extra text after the timestamp. If the timestamp were in a fixed format (like the one above) we could just hard-code it to grab the first two fields, or even the first N characters. However, in our case the format of the timestamp is user-controlled, so we're planning to let the user specify a custom time.Parse layout for their logs. We can hack around this with the following "introspect the error message" workaround (see runnable code at https://go.dev/play/p/CWuSk0te7-p): t, err := time.Parse(layout, line) if e, ok := err.(*time.ParseError); ok && strings.HasPrefix(e.Message, ": extra text: ") { prefix := line[:len(line)-len(e.ValueElem)] t, _ = time.Parse(layout, prefix) // parsing just the prefix should succeed err = nil } // use t, err This works, and it seems unlikely the Go team will change that "extra text" message, but that's certainly not guaranteed, and it's bad form to rely on the formatting of error messages. It also means we need to call time.Parse again, when it's already done the work once. Does anyone have suggestions for how to best parse "time prefixes"? Currently we're thinking of either the above hack, or copying the time.Parse code into our repo and modifying it to suit (there's a clear place that returns "extra text", so that would be annoying, but easy enough to do). This seems like it would be a useful feature for others, and I'm surprised there are not open issues about this already (I couldn't find any). Maybe I could open an issue to suggest that ParseError could have a new method ExtraText as follows: // ExtraText returns the extra text after the parsed time value in the original string. // If this error is not an "extra text" error, return "", nil. func (*ParseError) ExtraText() (extra string, parsed Time) But of course, even if that method were added, it would have to wait till at least Go 1.19, so for our project we need a way forward either way. Thanks, Ben -- 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 on the web visit https://groups.google.com/d/msgid/golang-nuts/790d818f-009c-42c2-9be6-b8cf6c170444n%40googlegroups.com.
