使用regexp解析Apache日志文件[重复]

Question

This question already has an answer here:

• Split a string on whitespace in Go? 3 answers

I am parsing an Apache log that I have customised to give me two values only: "time" and "memory" (the values are number of milliseconds and number of bytes) that are both are int64 or float64, but I am using regexp and Go to parse through the file, so when I am matching the contents of the files it return "[]" (empty braces) and is not populating the slice, my code is:

for _, line := range lines {
    var buffer bytes.Buffer

    buffer.WriteString(`\[0-9]+\s`)
    buffer.WriteString(`[0-9]+\s`)
    re1, err := regexp.Compile(buffer.String())

    if err != nil {
        log.Fatalf("regexp: %s", err)
    }
    result := re1.FindStringSubmatch(line)
    fmt.Println(result)
}

When I am printing result, it gives me empty braces and when I am running the whole program, it gives index out of range (which is understandable because result is empty).

My data looks like this:

1040 3952
2849 6832

</div>

Answer 1

Regexp is entirely the wrong tool for this job. It will be much easier to read, and much faster to operate, to just use strings.Split or strings.Fields:

for _, line := range lines {
    fields := strings.Fields(line)
    ms := fields[0]
    size := fields[1]
    fmt.Printf("time: %v, size: %v
", ms, size)
}

If you want to convert these to numbers, you can easily do so with the strconv package, with the additional benefit that it will detect if you get unexpected (non-numeric) input):

for _, line := range lines {
    fields := strings.Fields(line)
    ms, err := strconv.Itoa(fields[0])
    if err != nil {
        log.Fatalf("time field: %s", err)
    }
    size, err := strconv.Atoi(fields[1])
    if err != nil {
        log.Fatalf("size field: %s", err)
    }
    fmt.Printf("time: %v, size: %v
", ms, size)
}

---

If you do insist on using a regular expression, at least compile it only once, outside of your for loop:

re, err := regexp.Compile( ... )
if err != nil {
    log.Fatalf("regexp: %s", err)
}
for _, line := range lines {
    result := re.FindStringSubmatch(line)
    fmt.Println(result)
}