Use a select to monitor stdout

ioctl_linux.go

@@ -4,7 +4,7 @@
 package termenv
 
 import (
-	"fmt"
+	"syscall"
 	"time"
 
 	"golang.org/x/sys/unix"
@@ -14,22 +14,12 @@ func tcFlush(fd int, selector uintptr) error {
 	return unix.IoctlSetInt(fd, unix.TCFLSH, int(selector))
 }
 
-func waitForData(fd uintptr) error {
-	var avail int
-	var err error
+func waitForData(fd uintptr, timeout time.Duration) error {
+	tv := syscall.NsecToTimeval(int64(timeout))
 
-	for i := 1; i < 10; i++ {
-		avail, err = unix.IoctlGetInt(int(fd), unix.TIOCINQ)
-		if err != nil || avail > 0 {
-			break
-		}
+	var fds syscall.FdSet
+	fds.Bits[0] = 1 << uint(fd)
 
-		time.Sleep(time.Duration(i*i) * time.Millisecond)
-	}
-
-	if avail == 0 || err != nil {
-		return fmt.Errorf("timeout")
-	}
-
-	return nil
+	_, err := syscall.Select(int(fd)+1, &fds, nil, nil, &tv)
+	return err
 }

ioctl_other.go

@@ -4,13 +4,15 @@
 package termenv
 
 import (
+	"time"
+
 	"golang.org/x/sys/unix"
 )
 
 func tcFlush(fd int, selector uintptr) error {
 	return unix.IoctlSetInt(fd, unix.TCFLSH, int(selector))
 }
 
-func waitForData(fd uintptr) error {
+func waitForData(fd uintptr, timeout time.Duration) error {
 	return nil
 }

ioctl_unix.go

@@ -7,10 +7,8 @@
 package termenv
 
 import (
-	"fmt"
 	"syscall"
 	"time"
-	"unsafe"
 
 	"golang.org/x/sys/unix"
 )
@@ -24,22 +22,11 @@ func tcFlush(fd int, selector uintptr) error {
 	return unix.IoctlSetPointerInt(fd, unix.TIOCFLUSH, int(selector))
 }
 
-func waitForData(fd uintptr) error {
-	var avail int
-	var err syscall.Errno
+func waitForData(fd uintptr, timeout time.Duration) error {
+	tv := syscall.NsecToTimeval(int64(timeout))
 
-	for i := 1; i < 10; i++ {
-		_, _, err = syscall.Syscall(syscall.SYS_IOCTL, fd, _FIONREAD, uintptr(unsafe.Pointer(&avail)))
-		if err != 0 || avail > 0 {
-			break
-		}
+	var fds syscall.FdSet
+	fds.Bits[0] = 1 << uint(fd)
 
-		time.Sleep(time.Duration(i*i) * time.Millisecond)
-	}
-
-	if avail == 0 || err != 0 {
-		return fmt.Errorf("timeout")
-	}
-
-	return nil
+	return syscall.Select(int(fd)+1, &fds, nil, nil, &tv)
 }

termenv_unix.go

@@ -8,6 +8,7 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"golang.org/x/sys/unix"
 )
@@ -85,7 +86,7 @@ func backgroundColor() Color {
 }
 
 func readNextByte(f *os.File) (byte, error) {
-	if err := waitForData(f.Fd()); err != nil {
+	if err := waitForData(f.Fd(), 100*time.Millisecond); err != nil {
 		return 0, err
 	}