1 files changed, 48 insertions, 0 deletions
diff --git a/cwriter/writer_posix.go b/cwriter/writer_posix.go
new file mode 100644
index 0000000..e80d757
--- /dev/null
+++ b/cwriter/writer_posix.go
@@ -0,0 +1,48 @@
+//go:build !windows
+
+package cwriter
+
+import (
+	"bytes"
+	"io"
+
+	"golang.org/x/sys/unix"
+)
+
+// Writer is a buffered terminal writer, which moves cursor N lines up
+// on each flush except the first one, where N is a number of lines of
+// a previous flush.
+type Writer struct {
+	*bytes.Buffer
+	out      io.Writer
+	ew       escWriter
+	fd       int
+	terminal bool
+	termSize func(int) (int, int, error)
+}
+
+// Flush flushes the underlying buffer.
+// It's caller's responsibility to pass correct number of lines.
+func (w *Writer) Flush(lines int) error {
+	_, err := w.WriteTo(w.out)
+	// some terminals interpret 'cursor up 0' as 'cursor up 1'
+	if err == nil && lines > 0 {
+		err = w.ew.ansiCuuAndEd(w, lines)
+	}
+	return err
+}
+
+// GetSize returns the dimensions of the given terminal.
+func GetSize(fd int) (width, height int, err error) {
+	ws, err := unix.IoctlGetWinsize(fd, unix.TIOCGWINSZ)
+	if err != nil {
+		return -1, -1, err
+	}
+	return int(ws.Col), int(ws.Row), nil
+}
+
+// IsTerminal returns whether the given file descriptor is a terminal.
+func IsTerminal(fd int) bool {
+	_, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
+	return err == nil
+}