Golang : Display a text file line by line with line number example



Tags : golang read-text-file line-by-line strings-split ioutil-readfile

Problem:

Instead of using cat or more commands to display a text file line by line. You want to display the file content line by line with a number for each line in a terminal. You also want to know how many total lines are there in the text file. How to do that?

Solution:

Use this simple Golang program to display the text file content with line number on the right side.

countdisplaylines.go

 package main

 import (
 "fmt"
 "io/ioutil"
 "os"
 "strings"
 )

 func main() {
 if len(os.Args) <= 1 {
 fmt.Printf("USAGE : %s <target_filename> \n", os.Args[0])
 os.Exit(0)
 }

 fileName := os.Args[1]

 fileBytes, err := ioutil.ReadFile(fileName)

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 lines := strings.Split(string(fileBytes), "\n")

 // remove the last item from the lines slice
 // which is empty
 lines = lines[:len(lines)-1]

 // len() function will count the total number of lines
 fmt.Println(fileName, "has a total of", len(lines), "lines")
 for i, line := range lines {
 // i = i + 1 // uncomment to start from 1 instead of 0
 fmt.Println(i, line)
 }

 }

Sample output:

$ ./countdisplaylines 123.txt

123.txt has a total of 3 lines

0 one

1 two

2 three


content of the 123.txt file:

one

two

three

  See also : Golang : Write multiple lines or divide string into multiple lines



Tags : golang read-text-file line-by-line strings-split ioutil-readfile

By Adam Ng

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