README.md

Line by line writer

Thread-safe io.WriterCloser allowing you to write from different sources in one line by line. Writing to the source occurs only after the end of the line or the closing of the generated io.WriterCloser.

Example:

package main

import (
	"fmt"
	"os"
	"sync"
	"time"

	"github.com/evg4b/linebyline"
)

func main() {

	wg := sync.WaitGroup{}

	wr1 := linebyline.NewByLineWriter(
	    linebyline.WithOutWriter(os.Stdout),
	)
	wr2 := linebyline.NewByLineWriter(
	    linebyline.WithOutWriter(os.Stdout),
	)

	wg.Add(2)

	go func() {
		defer wg.Done()
		for i := 0; i < 50; i++ {
			fmt.Fprintf(wr1, "[#1] line %d ", i)
			// do something else ...
			time.Sleep(10 * time.Millisecond)

			fmt.Fprintln(wr1, "first writer")
		}
	}()

	go func() {
		defer wg.Done()
		for i := 0; i < 50; i++ {
			fmt.Fprintf(wr2, "[#2] line %d ", i)
			// do something else ...
			time.Sleep(20 * time.Millisecond)

			fmt.Fprintln(wr2, "second writer")
		}
	}()

	wg.Wait()

	err := w1.Close()
	if err != nil {
		panic(err)
	}

	err := w2.Close()
	if err != nil {
		panic(err)
	}
}

Output:

[#1] line 0 first writer
[#2] line 0 second writer
[#1] line 1 first writer
[#1] line 2 first writer
[#2] line 1 second writer
[#1] line 3 first writer
[#1] line 4 first writer
[#1] line 5 first writer
[#2] line 2 second writer
[#1] line 6 first writer
[#1] line 7 first writer
...

For not safe writers:

var writer bytes.Buffer
safeWriter := linebyline.NewSafeWriter(&writer)

wr1 := linebyline.NewByLineWriter(
    linebyline.WithOutWriter(safeWriter),
)
defer wr1.Close()

wr2 := linebyline.NewByLineWriter(
    linebyline.WithOutWriter(safeWriter),
)
defer wr2.Close()

fmt.Fprintln(wr1, "second writer")
fmt.Fprintln(wr2, "second writer")
// do something else ...

Use flush function

wr1 := linebyline.NewByLineWriter(
    linebyline.WithFlushFunc(func(bytes []byte) error {
        print(string(bytes))
        return nil
    }),
)
defer wr1.Close()

wr2 := linebyline.NewByLineWriter(
    linebyline.WithFlushFunc(func(bytes []byte) error {
        print(string(bytes))
        return nil
    }),
)
defer wr2.Close()

fmt.Fprintln(wr1, "second writer")
fmt.Fprintln(wr2, "second writer")
// do something else ...

Use custom end rune

wr1 := linebyline.NewByLineWriter(
    linebyline.WithOutWriter(os.Stdout),
    linebyline.WithEndRune('\t'),
)
defer wr1.Close()

wr2 := linebyline.NewByLineWriter(
    linebyline.WithOutWriter(os.Stdout),
    linebyline.WithEndRune('\t'),
)
defer wr2.Close()

fmt.Fprint(wr1, "second writer\t")
fmt.Fprint(wr2, "second writer\t")
// do something else ...

Use custom end rune

wr1 := linebyline.NewByLineWriter(
    linebyline.WithOutWriter(os.Stdout),
    linebyline.OmitNewLineRune(),
)
defer wr1.Close()

wr2 := linebyline.NewByLineWriter(
    linebyline.WithOutWriter(os.Stdout),
    linebyline.OmitNewLineRune(),
)
defer wr2.Close()

fmt.Fprintln(wr1, "second writer")
fmt.Fprintln(wr2, "second writer")
// do something else ...