Golang : Append content to a file
In this tutorial, we will learn how to open a file with specific mode such as for appending data when writing. This means that the operation depends on how the file is opened initially.
Example of appending content to a file :
appendfile.go
package main
import (
"os"
"fmt"
)
func main () {
// open files r and w
file, err := os.OpenFile("input.txt", os.O_APPEND|os.O_WRONLY,0600)
if err != nil {
panic(err)
}
defer file.Close()
if _, err = file.WriteString(" this is the APPENDED text"); err != nil {
panic(err)
}
fmt.Printf("Appended into file\n")
}
There is a reference at the page bottom on what os.O_APPEND
and os.O_WRONLY
parameters about.
Reference :
Extract from http://golang.org/src/pkg/os/file.go
// Flags to Open wrapping those of the underlying system. Not all flags
// may be implemented on a given system.
const (
O_RDONLY int = syscall.O_RDONLY // open the file read-only.
O_WRONLY int = syscall.O_WRONLY // open the file write-only.
O_RDWR int = syscall.O_RDWR // open the file read-write.
O_APPEND int = syscall.O_APPEND // append data to the file when writing.
O_CREATE int = syscall.O_CREAT // create a new file if none exists.
O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist
O_SYNC int = syscall.O_SYNC // open for synchronous I/O.
O_TRUNC int = syscall.O_TRUNC // if possible, truncate file when opened.
)
By Adam Ng
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