One less syscall in most cases

Author: karolba

main.go

@@ -17,7 +17,6 @@ import (
 
 	"github.com/alessio/shellescape"
 	"github.com/fatih/color"
-	"github.com/mattn/go-isatty"
 	"github.com/pkg/term/termios"
 	"golang.design/x/chann"
 	"golang.org/x/exp/slices"
@@ -35,8 +34,6 @@ var noLongerSpawnChildren = atomic.Bool{}
 var bold = color.New(color.Bold).SprintFunc()
 var yellow = color.New(color.FgYellow).SprintFunc()
 
-var stdoutIsTty = isatty.IsTerminal(uintptr(syscall.Stdout))
-
 func writeOut(out *Output) {
 	var clearedOutBytes int64
 
@@ -175,7 +172,7 @@ func displaySequentially(processes <-chan *ProcessResult) (exitCode int) {
 	var originalTermState *term.State
 	var err error
 
-	if stdoutIsTty {
+	if stdoutIsTty() {
 		originalTermState, err = term.GetState(syscall.Stdout)
 		if err != nil {
 			log.Printf("Warning: could get terminal state for stdout: %v\n", err)
@@ -199,7 +196,7 @@ func displaySequentially(processes <-chan *ProcessResult) (exitCode int) {
 		if *flVerbose {
 			quotedCommand := shellescape.QuoteCommand(processResult.originalCommand)
 
-			if firstProcess || !stdoutIsTty {
+			if firstProcess || !stdoutIsTty() {
 				_, _ = fmt.Fprintf(os.Stderr, bold("+ %s")+"\n", quotedCommand)
 			} else if !processResult.isAlive() {
 				_, _ = fmt.Fprintf(os.Stderr,

runner.go

@@ -313,14 +313,14 @@ func runWithStdin(command []string, stdin io.Reader) (result *ProcessResult) {
 
 	recursiveTaskLimitClient().addWait(result)
 
-	if stdoutIsTty {
+	if stdoutIsTty() {
 		command = append([]string{executable(), "--_execute-and-flush-tty"}, command...)
 	}
 
 	result.cmd = exec.Command(command[0], command[1:]...)
 	result.cmd.Stdin = stdin
 
-	if stdoutIsTty {
+	if stdoutIsTty() {
 		result.output = runInteractive(result.cmd)
 	} else {
 		result.output = runNonInteractive(result.cmd)

util.go

@@ -7,6 +7,8 @@ import (
 	"path/filepath"
 	"sync"
 	"syscall"
+
+	"github.com/mattn/go-isatty"
 )
 
 func max(a, b int) int {
@@ -24,6 +26,10 @@ func min(a, b int) int {
 	}
 }
 
+var stdoutIsTty = sync.OnceValue(func() bool {
+	return isatty.IsTerminal(uintptr(syscall.Stdout))
+})
+
 var dataDir = sync.OnceValue(func() (dir string) {
 	if _, err := os.Stat("/dev/shm"); !os.IsNotExist(err) {
 		dir = "/dev/shm"