使用fmt.Sscanf报unexpected EOF？

// Sscanf scans the argument string, storing successive space-separated

// values into successive arguments as determined by the format. It

// returns the number of items successfully parsed.

// Newlines in the input must match newlines in the format.

func Sscanf(str string, format string, a ...any) (n int, err error) {

return Fscanf((*stringReader)(&str), format, a...)

}

// Sscanf scans the argument string, storing successive space-separated // values into successive arguments as determined by the format. It // returns the number of items successfully parsed. // Newlines in the input must match newlines in the format.

当你执行下面代码会发现，第一个a把剩余所有字符串都获取了

package main

import (
    "fmt"
    "log"
)

func main() {
    var (
        str    = "a=aaa,b=bbb,c=ccc"
        format = "a=%s,b=%s,c=%s"

        a string
        b string
        c string
    )

    if _, err := fmt.Sscanf(str, format, &a, &b, &c); err != nil {
        log.Println(err)
    }

    log.Println("a:", a)
    log.Println("b:", b)
    log.Println("c:", c)
}

结果如下

2022/09/21 17:50:04 unexpected EOF
2022/09/21 17:50:04 a: aaa,b=bbb,c=ccc
2022/09/21 17:50:04 b:
2022/09/21 17:50:04 c:

你可以增加空格，因为scanf默认都是已空格或者制表符之类的作为分隔，下面这种方式需要两种字符串都已空格分开

package main

import (
    "fmt"
    "log"
)

func main() {
    var (
        str    = "a=aaa ,b=bbb ,c=ccc"
        format = "a=%s ,b=%s ,c=%s"

        a string
        b string
        c string
    )

    if _, err := fmt.Sscanf(str, format, &a, &b, &c); err != nil {
        log.Println(err)
    }

    log.Println("a:", a)
    log.Println("b:", b)
    log.Println("c:", c)
}

结果如下
2022/09/21 17:54:58 a: aaa
2022/09/21 17:54:58 b: bbb
2022/09/21 17:54:58 c: ccc

下面方法我将扫描分隔符改为逗号，完全满足你的需求

package main

import (
    "fmt"
    "log"
)

func main() {
    var (
        str    = "a=aaa,b=bbb,c=ccc"
        format = "a=%s,b=%s,c=%s"

        a, b, c string
    )

    if _, err := fmt.Sscanf(str, format, (*mm)(&a), (*mm)(&b), (*mm)(&c)); err != nil {
        log.Println(err)
    }

    log.Println("a:", a)
    log.Println("b:", b)
    log.Println("c:", c)
}

type mm string

func (m *mm) Scan(state fmt.ScanState, verb rune) error {
    tok, err := state.Token(true, func(r rune) bool {
        return r != ',' // 默认string以空格分隔,我这里改为用逗号分隔
    })
    if err != nil {
        return err
    }
    *m = mm(tok)
    return nil
}


结果如下

2022/09/21 17:55:28 a: aaa
2022/09/21 17:55:28 b: bbb
2022/09/21 17:55:28 c: ccc

我又修改了下，感觉把类型改为自定义使用起来比较麻烦。这下更完美了。

@Mericusta @yecz