The Writer will send data when the buffer is either full or when explicitly flushed. go version go version go1.18.1 linux/amd64 We use Go version 1.18. func (f File) WriteString (s string) (n int, err error) The functions that we use typically return the number of bytes written and an error, if any. Moreover, this function is defined under the io package. And if w is implemented by StringWriter then its WriteString method is called immediately. You’ll note the use of bufio NewWriter and method Writer.Flush. To write to files in Go, we use the os, ioutil, and fmt packages. The WriteString () function in Go language is used to write the contents of the stated string s to the writer w, which takes a slice of bytes. Overwrite file if it exists: file, err := os.OpenFile('/path/to/file', os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)Ĭreate file if it doesn’t exist, else append to it: file, err := os.OpenFile('/path/to/file', os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644) Write a text file line-by-line full exampleīelow is a common example writing a text file line by line in Golang. One of the first three flags below must be provided in the OpenFile function. The Golang OS package OpenFile function opens files using flags and permissions. A buffered writer queues up bytes until a threshold is reach then completes the write operation to minimize resources.

The bufio package provides an efficient buffered writer.

Golang write to file