Go 正则匹配之跨行匹配

跨行匹配

一般正则匹配默认是按行来进行匹配的，如果要跨行匹配，需要使用 `(?s)` 来启用多行模式。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."// fmt.Println(data)// re := regexp.MustCompile(`line.*And`)re := regexp.MustCompile(`(?s)line.*And`)match := re.FindString(data)fmt.Println(match)out := re.ReplaceAllString(data, "------")fmt.Println(out)
}

line. 
And
This is the first ------ this is the second line.

go 正则匹配相关的其他常用函数

Compile、MustCompile

同样的功能，不同的设计：

Compile函数基于错误处理设计，将正则表达式编译成有效的可匹配格式，适用于用户输入场景。当用户输入的正则表达式不合法时，该函数会返回一个错误。
MustCompile函数基于异常处理设计，适用于硬编码场景。当调用者明确知道输入不会引起函数错误时，要求调用者检查这个错误是不必要和累赘的。我们应该假设函数的输入一直合法，当调用者输入了不应该出现的输入时，就触发panic异常。

其实直接从 MustCompile 的实现可以看出，MustCompile 本质上是调用的 Compile ，如果表达式编译失败，直接 panic ，而 Compile 则会把 err 返回，由用户决定是否 panic 或进行其他处理：

// MustCompile is like Compile but panics if the expression cannot be parsed.
// It simplifies safe initialization of global variables holding compiled regular
// expressions.
func MustCompile(str string) *Regexp {regexp, err := Compile(str)if err != nil {panic(`regexp: Compile(` + quote(str) + `): ` + err.Error())}return regexp
}

FindString

FindString 用来返回匹配到的第一个字符串。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindString(data)fmt.Println(match) // the first line
}

FindAllString

FindString 用来返回匹配到的所有的字符串。用户可以指定想要返回的匹配到的字符串的个数。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindAllString(data, 3)fmt.Printf("%#v\n", match) // []string{"the first line", "the second line"}
}

Find

类似于FindString，只不过以字节数组的形式表示。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.Find([]byte(data))// match := re.FindAll([]byte(data), 3)fmt.Printf("%#v\n", match)         // []byte{0x74, 0x68, 0x65, 0x20, 0x66, 0x69, 0x72, 0x73, 0x74, 0x20, 0x6c, 0x69, 0x6e, 0x65}fmt.Printf("%#v\n", string(match)) // "the first line"
}

FindAll

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)// match := re.Find([]byte(data))match := re.FindAll([]byte(data), 3)fmt.Printf("%#v\n", match) // [][]uint8{[]uint8{0x74, 0x68, 0x65, 0x20, 0x66, 0x69, 0x72, 0x73, 0x74, 0x20, 0x6c, 0x69, 0x6e, 0x65}, []uint8{0x74, 0x68, 0x65, 0x20, 0x73, 0x65, 0x63, 0x6f, 0x6e, 0x64, 0x20, 0x6c, 0x69, 0x6e, 0x65}}
}

FindIndex

返回匹配字符串的起始位置和结束位置索引，未匹配到的话返回 nil

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindIndex([]byte(data))// match := re.FindAll([]byte(data), 3)fmt.Printf("%#v\n", match)                   // []int{8, 22}if match == nil {fmt.Println("match is nil")return}fmt.Printf("%#v\n", data[match[0]:match[1]]) // "the first line"
}

临时插入一个小知识，声明一个未初始化的 Array 或 Map ，其值初始为 nil。

package mainimport ("fmt"
)func main() {var a []intfmt.Printf("%#v\n", a) // []int(nil)fmt.Println(a == nil)  // truea = []int{}fmt.Printf("%#v\n", a) // []int{}fmt.Println(a == nil)  // falsevar m map[string]stringfmt.Printf("%#v\n", m) // map[string]string(nil)fmt.Println(m == nil)  // truem = map[string]string{}fmt.Printf("%#v\n", m) // map[string]string{}fmt.Println(m == nil)  // false
}

FindAllIndex

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindAllIndex([]byte(data), 3)// match := re.FindAll([]byte(data), 3)fmt.Printf("%#v\n", match) // [][]int{[]int{8, 22}, []int{37, 52}}if match == nil {fmt.Println("match is nil")return}for _, m := range match {fmt.Printf("%#v\n", data[m[0]:m[1]]) // "the first line"  "the second line"}
}

FindSubMatch

有些例子比较简单，就不多描述了

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindSubmatch([]byte(data))fmt.Printf("%#v\n", match) // [][]uint8{[]uint8{0x74, 0x68, 0x65, 0x20, 0x66, 0x69, 0x72, 0x73, 0x74, 0x20, 0x6c, 0x69, 0x6e, 0x65}}
}

FindAllSubMatch

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindAllSubmatch([]byte(data), 3)fmt.Printf("%#v\n", match) // [][][]uint8{[][]uint8{[]uint8{0x74, 0x68, 0x65, 0x20, 0x66, 0x69, 0x72, 0x73, 0x74, 0x20, 0x6c, 0x69, 0x6e, 0x65}}, //             [][]uint8{[]uint8{0x74, 0x68, 0x65, 0x20, 0x73, 0x65, 0x63, 0x6f, 0x6e, 0x64, 0x20, 0x6c, 0x69, 0x6e, 0x65}}}
}

FindStringSubMatch

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindStringSubmatch(data)fmt.Printf("%#v\n", match) // []string{"the first line"}
}

FindAllStringSubMatch

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.FindAllStringSubmatch(data, 3)fmt.Printf("%#v\n", match) // [][]string{[]string{"the first line"}, []string{"the second line"}}
}

ReplaceAllString

将所有匹配到的字符串使用给定字符串进行替换。替换的字符可以引用匹配组的内容。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the (.*) line`)out := re.ReplaceAllString(data, "$1") fmt.Printf("%#v\n", out) // "This is first. \nAnd this is second."
}

ReplaceAllFunc

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)out := re.ReplaceAllFunc([]byte(data), func(bytes []byte) []byte {return []byte("[" + string(bytes) + "]")})fmt.Printf("%#v\n", out)         // []byte{0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x5b, 0x74, 0x68, 0x65, 0x20, 0x66, 0x69, 0x72, 0x73, 0x74, 0x20, 0x6c, 0x69, 0x6e, 0x65, 0x5d, 0x2e, 0x20, 0xa, 0x41, 0x6e, 0x64, 0x20, 0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x5b, 0x74, 0x68, 0x65, 0x20, 0x73, 0x65, 0x63, 0x6f, 0x6e, 0x64, 0x20, 0x6c, 0x69, 0x6e, 0x65, 0x5d, 0x2e}fmt.Printf("%#v\n", string(out)) // "This is [the first line]. \nAnd this is [the second line]."
}

ReplaceAllStringFunc

可以编写函数来决定如何替换掉匹配到的字符串，其中匿名函数中参数 s 为匹配到的字符串。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)out := re.ReplaceAllStringFunc(data, func(s string) string {return "[" + s + "]"})fmt.Printf("%#v\n", out) // "This is [the first line]. \nAnd this is [the second line]."
}

ReplaceAllLiteral

通过字面量替换，以字节数组的形式。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the (.*) line`)out := re.ReplaceAllLiteral([]byte(data), []byte("$1"))fmt.Printf("%#v\n", out)         // []byte{0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x24, 0x31, 0x2e, 0x20, 0xa, 0x41, 0x6e, 0x64, 0x20, 0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x24, 0x31, 0x2e}fmt.Printf("%#v\n", string(out)) // "This is $1. \nAnd this is $1."
}

ReplaceAllLiteralString

替换的字符串被当作字符串字面量进行处理。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the (.*) line`)out := re.ReplaceAllLiteralString(data, "$1")fmt.Printf("%#v\n", out) // "This is $1. \nAnd this is $1."
}

ReplaceAll

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)out := re.ReplaceAll([]byte(data), []byte("---replace string---"))fmt.Printf("%#v\n", out)         // []byte{0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x2d, 0x2d, 0x2d, 0x72, 0x65, 0x70, 0x6c, 0x61, 0x63, 0x65, 0x20, 0x73, 0x74, 0x72, 0x69, 0x6e, 0x67, 0x2d, 0x2d, 0x2d, 0x2e, 0x20, 0xa, 0x41, 0x6e, 0x64, 0x20, 0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x2d, 0x2d, 0x2d, 0x72, 0x65, 0x70, 0x6c, 0x61, 0x63, 0x65, 0x20, 0x73, 0x74, 0x72, 0x69, 0x6e, 0x67, 0x2d, 0x2d, 0x2d, 0x2e}fmt.Printf("%#v\n", string(out)) // "This is ---replace string---. \nAnd this is ---replace string---."
}

MatchString

正则模式是否有匹配到字符串。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.MatchString(data)fmt.Printf("%#v\n", match) // truere = regexp.MustCompile(`the x.* line`)match = re.MatchString(data)fmt.Printf("%#v\n", match) // false
}

Match

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)match := re.Match([]byte(data))fmt.Printf("%#v\n", match) // truere = regexp.MustCompile(`the x.* line`)match = re.Match([]byte(data))fmt.Printf("%#v\n", match) // false
}

Split

将正则匹配到的字符串作为分隔符，对原字符串进行 Split 分隔，返回分隔后生成的数据。用户可以指定分隔后数组的长度（不超过全部分隔后的数组长度）。

package mainimport ("fmt""regexp"
)func main() {data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the .* line`)out := re.Split(data, 1)fmt.Printf("%#v\n", out) // []string{"This is the first line. \nAnd this is the second line."}out = re.Split(data, 2)fmt.Printf("%#v\n", out) // []string{"This is ", ". \nAnd this is the second line."}out = re.Split(data, 3)fmt.Printf("%#v\n", out) // []string{"This is ", ". \nAnd this is ", "."}out = re.Split(data, 4)fmt.Printf("%#v\n", out) // []string{"This is ", ". \nAnd this is ", "."}
}

NumSubexp

返回正则模式子组的数目

package mainimport ("fmt""regexp"
)func main() {// data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the (.*) lin()e`)// out := re.FindString(data)// fmt.Printf("%#v\n", out)fmt.Printf("%#v\n", re.NumSubexp()) // 2
}

LiteralPrefix

返回所有匹配项都共同拥有的前缀（去除可变元素）

prefix：共同拥有的前缀

complete：如果 prefix 就是正则表达式本身，则返回 true，否则返回 false

package mainimport ("fmt""regexp"
)func main() {// data := "This is the first line. \nAnd this is the second line."re := regexp.MustCompile(`the (.*) line`)prefix, complete := re.LiteralPrefix()fmt.Printf("%#v\n", prefix)   // "the "fmt.Printf("%#v\n", complete) // falsere = regexp.MustCompile(`the line`)prefix, complete = re.LiteralPrefix()fmt.Printf("%#v\n", prefix)   // "the line"fmt.Printf("%#v\n", complete) // true
}