runner: pipe commands together

internal/runner/runner.go

@@ -1,6 +1,7 @@
 package runner
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"os/exec"
@@ -26,3 +27,33 @@ func (runner *ZRunner) Run(ctx context.Context, command string, formatArgs ...an
 	cmd := exec.Command(runner.Prog, args...)
 	return cmd.CombinedOutput()
 }
+
+func Pipeline(cmds ...*exec.Cmd) ([]byte, error) {
+	for i := 0; i < len(cmds)-1; i++ {
+		stdout, err := cmds[i].StdoutPipe()
+		if err != nil {
+			return nil, err
+		}
+		cmds[i+1].Stdin = stdout
+	}
+
+	out := bytes.Buffer{}
+
+	cmds[len(cmds)-1].Stdout = &out
+
+	for _, cmd := range cmds {
+		err := cmd.Start()
+		if err != nil {
+			return out.Bytes(), err
+		}
+	}
+
+	for _, cmd := range cmds {
+		err := cmd.Wait()
+		if err != nil {
+			return out.Bytes(), err
+		}
+	}
+
+	return out.Bytes(), nil
+}

internal/runner/runner_test.go

@@ -2,9 +2,11 @@ package runner_test
 
 import (
 	"context"
+	"os/exec"
 	"testing"
 
 	"git.gentoo.party/sam/thanks/internal/runner"
+	"github.com/stretchr/testify/assert"
 )
 
 func Test_ZCommand(t *testing.T) {
@@ -19,3 +21,12 @@ func Test_ZCommand(t *testing.T) {
 		t.Errorf("localRunner failed: %s\n\n%s", err.Error(), out)
 	}
 }
+
+func Test_Pipelie(t *testing.T) {
+	c1 := exec.Command("echo", "-n", "foo")
+	c2 := exec.Command("rev")
+	out, err := runner.Pipeline(c1, c2)
+
+	assert.Equal(t, "oof", string(out))
+	assert.Nil(t, err)
+}