1 files changed, 23 insertions, 0 deletions
diff --git a/internal/cli/termwidth_unix.go b/internal/cli/termwidth_unix.go
new file mode 100644
index 0000000..9d1b47d
--- /dev/null
+++ b/internal/cli/termwidth_unix.go
@@ -0,0 +1,23 @@
+//go:build unix
+
+package cli
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// ttyWidth returns f's terminal column width via the TIOCGWINSZ ioctl, or 0
+// if f isn't a terminal (redirected to a file/pipe, as in tests) or the
+// ioctl fails.
+func ttyWidth(f *os.File) int {
+	var ws struct {
+		Row, Col, Xpixel, Ypixel uint16
+	}
+	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), syscall.TIOCGWINSZ, uintptr(unsafe.Pointer(&ws)))
+	if errno != 0 || ws.Col == 0 {
+		return 0
+	}
+	return int(ws.Col)
+}