Golang : Read data from config file and assign to variables



Tags : golang read-file configuration parameters

Usually a large program will need multiple parameters to function properly and the parameters will determine the behavior of the program. A good programmer will make his or her program to accept parameters from command line, environment or read from a file.

In this tutorial, we will learn how to read data from a plain text config file - simulating a program reading parameters from a file.

Here you go!

 package main

 import (
  "bufio"
  "fmt"
  "io"
  "os"
  "strings"
 )

 type Config map[string]string

 func ReadConfig(filename string) (Config, error) {
 // init with some bogus data
  config := Config{
 "port": "8888",
 "password": "abc123",
 "ip": "127.0.0.1",
  }
  if len(filename) == 0 {
 return config, nil
  }
  file, err := os.Open(filename)
  if err != nil {
 return nil, err
  }
  defer file.Close()
  
  reader := bufio.NewReader(file)
  
  for {
 line, err := reader.ReadString('\n')
 
 // check if the line has = sign
 // and process the line. Ignore the rest.
 if equal := strings.Index(line, "="); equal >= 0 {
 if key := strings.TrimSpace(line[:equal]); len(key) > 0 {
 value := ""
 if len(line) > equal {
 value = strings.TrimSpace(line[equal+1:])
 }
 // assign the config map
 config[key] = value
 }
 }
 if err == io.EOF {
 break
 }
 if err != nil {
 return nil, err
 }
  }
  return config, nil
 }

 func main() {
 // for this tutorial, we will hard code it to config.txt
  config, err := ReadConfig(`config.txt`)

  if err != nil {
 fmt.Println(err)
  }

  //fmt.Println("Config data dump :", config)

  // assign values from config file to variables
  ip := config["ip"]
  pass := config["password"]
  port := config["port"]

  fmt.Println("IP :", ip)
  fmt.Println("Port :", port)
  fmt.Println("Password :", pass)
 }

Reading a sample config.txt file :

 [profile manager]
 key=value
 password = sjssh31mmv
 ; a comment
 port = 8080
 ip = 123.456.789.321
 # another comment
 url=example.com
 file=
 # last comment

Sample output :

IP : 123.456.789.321

Port : 8080

Password : sjssh31mmv



Tags : golang read-file configuration parameters

By Adam Ng

IF you gain some knowledge or the information here solved your programming problem. Please consider donating to the less fortunate or some charities that you like. Apart from donation, planting trees, volunteering or reducing your carbon footprint will be great too.


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