去正则表达式查找子字符串

Question

I have a string:

s := "root 1 12345 /root/pathtomyfolder/jdk/jdk.1.8.0.25 org.catalina.startup"

I need to grep the version number to a string

Tried,

var re = regexp.MustCompile(`jdk.*`)
func main() {
matches := re.FindStringSubmatch(s)
fmt.Printf ("%q", matches)
}

Answer 1

You need to specify capturing groups to extract submatches, as described in the package overview :

If 'Submatch' is present, the return value is a slice identifying the successive submatches of the expression. Submatches are matches of parenthesized subexpressions (also known as capturing groups) within the regular expression, numbered from left to right in order of opening parenthesis. Submatch 0 is the match of the entire expression, submatch 1 the match of the first parenthesized subexpression, and so on.

Something along the lines of the following:

func main() {
    var re = regexp.MustCompile(`jdk\.([^ ]+)`)
    s := "root 1 12345 /root/pathtomyfolder/jdk/jdk.1.8.0.25 org.catalina.startup"
    matches := re.FindStringSubmatch(s)
    fmt.Printf("%s", matches[1])
    // Prints: 1.8.0.25
}

You'll of course want to check whether there actually is a submatch, or matches[1] will panic.

Answer 2

如果您需要在其他地方使用/操作字符串变量中的值，您可以在 Marc 给出的给定示例中添加以下内容：

a := fmt.Sprintf("%s", matches[1])