How to append text to a file in Golang?
The OpenFile function with os.O_APPEND opens the already exist file test.txt in append mode. WriteString function write the content at the end of the file.
Example
package main
import (
"io/ioutil"
"log"
"fmt"
"os"
)
func AppendFile() {
file, err := os.OpenFile("test.txt", os.O_WRONLY|os.O_APPEND, 0644)
if err != nil {
log.Fatalf("failed opening file: %s", err)
}
defer file.Close()
len, err := file.WriteString(" The Go language was conceived in September 2007 by Robert Griesemer, Rob Pike, and Ken Thompson at Google.")
if err != nil {
log.Fatalf("failed writing to file: %s", err)
}
fmt.Printf("\nLength: %d bytes", len)
fmt.Printf("\nFile Name: %s", file.Name())
}
func ReadFile() {
data, err := ioutil.ReadFile("test.txt")
if err != nil {
log.Panicf("failed reading data from file: %s", err)
}
fmt.Printf("\nLength: %d bytes", len(data))
fmt.Printf("\nData: %s", data)
fmt.Printf("\nError: %v", err)
}
func main() {
fmt.Printf("######## Append file #########\n")
AppendFile()
fmt.Printf("\n\n######## Read file #########\n")
ReadFile()
}
Output
######## Append file #########
Length: 107 bytes
File Name: test.txt
######## Read file #########
Length: 246 bytes
Data: The Go Programming Language, also commonly referred to as Golang, is a general-purpose programming language, developed by a team at Google. The Go language was conceived in September 2007 by Robert Griesemer, Rob Pike, and Ken Thompson at Google.
Error:
Most Helpful This Week
Get Set and Clear Session in Golang
How to convert Colorful PNG image to Gray-scale?
Regular expression to extract all Non-Alphanumeric Characters from a String
How to check string contains uppercase lowercase character in Golang?
What is Rune? How to get ASCII value of any character in Go?
Example to use Weekday and YearDay function
How to create Empty and Nil Slice?
Golang Convert String into Snake Case
Catch values from Goroutines
Example to create custom error