Analysis and solution of golang file content coverage problem

Project scenario:

Read the database site mapping configuration through golang, generate nginx conf files, and check and restart nginx services, which has achieved the purpose of site automation deployment.

Problem description

When the content in the target file is very long and the content written is very short, the content of the target file cannot be completely overwritten.

package main

import (
	"os"
)

func ConfWrite() error {
	config := confTemplate()
	fileName := "/Users/test/Documents/"
	f, err := (fileName, os.O_CREATE|os.O_RDWR, 0666)
	if err != nil {
		return err
	}

	defer ()
	if _, err = (config); err != nil {
		return err
	}
	return nil
}

func confTemplate() string {
	return `
    <<listenPort>>

	server
    {
        listen 80;
        listen 443 ssl;
        server_name ;
        location / {
                <<proxyPass>>
                root /data/test;
        }
    }`
}

func main() {
	_ = ConfWrite()
}

Cause analysis:

This analysis may not be correct. Please find the exact cause in the future and add it.

(fileName, os.O_CREATE|os.O_RDWR, 0666) When this function opens a file, the length of the buffer is determined by the content of the original file. If the str content written using (str) is shorter than the length of the original file buffer, part of the content at the end of the original file will be retained. The effect of full coverage is not achieved. If the str content is longer than the length of the original file buffer, the original file will be completely overwritten.

Solution:

Add os.O_TRUNC and clear the file.

(fileName, os.O_CREATE|os.O_RDWR|os.O_TRUNC, 0666)

Summarize

This is the article about the analysis and solution of golang file content coverage. For more related golang file content coverage, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!