Go语言strings.TrimRight函数结果不符预期，为何输出Hell而非Hello？

Let's break down what's happening here—your confusion comes from misunderstanding how strings.TrimRight works in Go. It doesn't match and remove the entire cutset string from the end; instead, it removes individual characters from the end as long as they're present in the cutset, stopping only when it hits a character that's not in the set.

First, let's recap your code:

package main

import (
    "fmt"
    "strings"
)

func main() {
    result := strings.TrimRight("Hello Gophers", " Gophers")
    fmt.Println(result, len(result)) // Output: Hell 4
}

Step-by-step breakdown of the trimming process #

Your input string is "Hello Gophers", and the cutset " Gophers" includes these characters: ' ', 'G', 'o', 'p', 'h', 'e', 'r', 's'. Here's how trimming proceeds from the end:

1. 's' is in the cutset → remove it → "Hello Gopher"
2. 'r' is in the cutset → remove it → "Hello Gophe"
3. 'e' is in the cutset → remove it → "Hello Goph"
4. 'h' is in the cutset → remove it → "Hello Gop"
5. 'p' is in the cutset → remove it → "Hello Go"
6. 'o' is in the cutset → remove it → "Hello G"
7. 'G' is in the cutset → remove it → "Hello "
8. ' ' is in the cutset → remove it → "Hello"
9. The last character now is 'o'—which is also in the cutset (since "Gophers" contains 'o') → remove it → "Hell"
10. Next character is 'l', which isn't in the cutset → trimming stops.

That's why you end up with "Hell"—the final 'o' in "Hello" is part of your cutset, so it gets trimmed too.

The fix: Use strings.TrimSuffix for exact suffix removal #

If your goal is to remove the exact suffix " Gophers" from the string, strings.TrimSuffix is the right tool. It checks if the string ends with the specified suffix and removes it only if there's an exact match:

package main

import (
    "fmt"
    "strings"
)

func main() {
    result := strings.TrimSuffix("Hello Gophers", " Gophers")
    fmt.Println(result, len(result)) // Output: Hello 5
}

内容的提问来源于stack exchange，提问作者Tahseen