How to escape % in golang

In recent years, with the continuous development and popularization of the Internet industry, programming languages ​​have become increasingly important. Among many programming languages, Golang is favored by developers for its fast, efficient and safe performance advantages.

Although Golang has efficient performance, it will also encounter various problems and challenges. One of the common problems is the escape characters in Golang, especially the escape character "%".

In Golang, if you need to use the escape character "%", you need to repeat it twice, that is, "%%". This is because in Golang, the percent sign "%" itself is a Escape characters. Therefore, when Golang handles a string containing the percent sign "%", it will treat it as a format string and parse the parameters following it as format parameters.

For example, if you need to print the string "10%" in Golang, you need to write it as "fmt.Printf("10%%")". Here, the first percent sign "%" represents the escape character, and the second percent sign "%" represents the actual percent sign to be output.

If you directly write "fmt.Printf("10%")", Golang will think that you want to format the output and will look for the following parameters for output, so incorrect results will appear. This is because Golang will parse the characters after the percent sign "%" as part of the formatted string and does not correctly handle the percent sign itself.

Similar to this problem, there is a common error - the percent sign problem when encoding the URL. In HTTP requests, the percent sign in the URL generally represents an escape character, converting some special characters or bytes into some specially encoded strings. For example, represents a space and : represents a colon.

In Golang, you will also encounter percent sign problems when URL encoding. If you use Golang's own URL encoding function for encoding, you also need to pay attention to escaping the percent sign. For example, use the Encode function in "net/url" to encode a string in Golang:

import "net/url"

encodeStr := url.QueryEscape("http://www.baidu.com/?query=测试&name=百度")
fmt.Println(encodeStr) // 输出：http%3A%2F%2Fwww.baidu.com%2F%3Fquery%3D%E6%B5%8B%E8%AF%95%26name%3D%E7%99%BE%E5%BA%A6

As you can see, Golang escapes all special characters in the parameters and uses percent number to encode it.

However, if you want to introduce custom escape characters, such as the percent sign "%" mentioned earlier, Golang will cause decoding errors. For example, the following code will cause an error:

import "net/url"

encodeStr := url.QueryEscape("http://www.baidu.com/?query=测试&name=10%")
fmt.Println(encodeStr) // 输出：http%3A%2F%2Fwww.baidu.com%2F%3Fquery%3D%E6%B5%8B%E8%AF%95%26name%3D10

As you can see, only "10" is left in the "10%" in the encoding result. Characters will be lost during decoding, causing the program to An error occurred.

The solution to this situation is also very simple, just replace the characters that need to be escaped with other characters. For example, replace the percent sign "%" with "%" (the URL encoding of the percent sign):

import "net/url"
import "strings"

encodeStr := url.QueryEscape(strings.Replace("http://www.baidu.com/?query=测试&name=10%", "%", "%25", -1))
fmt.Println(encodeStr) // 输出：http%3A%2F%2Fwww.baidu.com%2F%3Fquery%3D%E6%B5%8B%E8%AF%95%26name%3D10%25

In this way, the encoding result will be decoded correctly.

In general, the escape character "%" in Golang requires special attention and needs to be repeated twice to use it correctly. When encoding URLs, if you need to use percent signs for escaping, special processing is required to avoid decoding errors. Only in this way can we take full advantage of Golang, avoid unexpected errors, and make our code more robust and efficient.

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