gream

README.md

gream

I was curious about how hard it would be to implement something like pypipe[1] in go. Turns out, not that hard.

[1] https://github.com/bugen/pypipe

example

$ echo "foo bar" | go run main.go 4
b

go.mod

module gream

go 1.21.3

require github.com/traefik/yaegi v0.15.1

go.sum

github.com/traefik/yaegi v0.15.1 h1:YA5SbaL6HZA0Exh9T/oArRHqGN2HQ+zgmCY7dkoTXu4=
github.com/traefik/yaegi v0.15.1/go.mod h1:AVRxhaI2G+nUsaM1zyktzwXn69G3t/AuTDrCiTds9p0=

main.go

package main

// silly pypipe poc in go: https://github.com/bugen/pypipe
// 2023 @leonjza

import (
	"os"
	"strings"

	"github.com/traefik/yaegi/interp"
	"github.com/traefik/yaegi/stdlib"
)

func main() {

	var col string

	if len(os.Args) <= 1 {
		col = "0"
	} else {
		col = os.Args[1]
	}

	i := interp.New(interp.Options{})
	i.Use(stdlib.Symbols)

	_, err := i.Eval(`import "bufio"`)
	if err != nil {
		panic(err)
	}
	_, err = i.Eval(`import "fmt"`)
	if err != nil {
		panic(err)
	}
	_, err = i.Eval(`import "os"`)
	if err != nil {
		panic(err)
	}
	_, err = i.Eval(`import "strings"`)
	if err != nil {
		panic(err)
	}

	lineProcessor := `
	s := bufio.NewScanner(os.Stdin)

	for s.Scan() {
		l := strings.TrimSpace(s.Text())
		fmt.Println(string(l[COLUMN]))
	}
	`

	lineProcessor = strings.Replace(lineProcessor, `COLUMN`, col, 1)

	_, err = i.Eval(lineProcessor)
	if err != nil {
		panic(err)
	}
}