feat: Add cmd that seeks to specific location in tape

cmd/stfs-seek/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"flag"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// See https://github.com/benmcclelland/mtio/blob/f929531fb4fe6433f7198ccd89d1c1414ef8fa3f/mtst.go#L46
+const (
+	MTIOCTOP = 0x40086d01 // Do magnetic tape operation
+	MTSEEK   = 22         // Seek to block
+)
+
+// Operation is struct for MTIOCTOP
+type Operation struct {
+	op int16 // Operation ID
+
+	pad int16 // Padding to match C structures
+
+	count int32 // Operation count
+}
+
+func main() {
+	file := flag.String("file", "/dev/nst0", "File of tape drive to open")
+	record := flag.Int("record", 0, "Record to seek too")
+
+	flag.Parse()
+
+	f, err := os.OpenFile(*file, os.O_RDONLY, os.ModeCharDevice)
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+
+	syscall.Syscall(
+		syscall.SYS_IOCTL,
+		f.Fd(),
+		MTIOCTOP,
+		uintptr(unsafe.Pointer(
+			&Operation{
+				op:    MTSEEK,
+				count: int32(*record),
+			},
+		)),
+	)
+}