kovidgoyal/kitty · error

Failed to seek in image data output file: %s with error: %w

Error message

Failed to seek in image data output file: %s with error: %w

What it means

transmit_shm opened the frame file successfully but the Seek to the end (to determine data size) failed. The file's size can't be established, so transmission aborts.

Source

Thrown at kittens/icat/transmit.go:95

		if frame.compose_onto > 0 {
			gc.SetOverlaidFrame(uint64(frame.compose_onto))
		}
		gc.SetLeftEdge(uint64(frame.left)).SetTopEdge(uint64(frame.top))
	}
	return gc
}

func transmit_shm(imgd *image_data, frame_num int, frame *image_frame) (err error) {
	var mmap shm.MMap
	var data_size int64
	if frame.in_memory_bytes == nil {
		f, err := os.Open(frame.filename)
		if err != nil {
			return fmt.Errorf("Failed to open image data output file: %s with error: %w", frame.filename, err)
		}
		defer f.Close()
		if data_size, err = f.Seek(0, io.SeekEnd); err != nil {
			return fmt.Errorf("Failed to seek in image data output file: %s with error: %w", frame.filename, err)
		}
		if _, err = f.Seek(0, io.SeekStart); err != nil {
			return fmt.Errorf("Failed to seek in image data output file: %s with error: %w", frame.filename, err)
		}
		if mmap, err = shm.CreateTemp("icat-*", uint64(data_size)); err != nil {
			return fmt.Errorf("Failed to create a SHM file for transmission: %w", err)
		}
		if _, err = io.ReadFull(f, mmap.Slice()); err != nil {
			mmap.Close()
			mmap.Unlink()
			return fmt.Errorf("Failed to read data from image output data file: %w", err)
		}
	} else {
		data_size = int64(len(frame.in_memory_bytes))
		if mmap, err = shm.CreateTemp("icat-*", uint64(data_size)); err != nil {
			return fmt.Errorf("Failed to create a SHM file for transmission: %w", err)
		}
		copy(mmap.Slice(), frame.in_memory_bytes)

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Ensure the frame file is a regular file, not a pipe
2. Keep encoded frames in memory (in_memory_bytes path) instead of files when possible
3. Check filesystem health if seeking regularly fails

if fi, err := os.Stat(f); err != nil || !fi.Mode().IsRegular() { /* reject pipes/special files */ }

if err != nil && strings.Contains(err.Error(), "Failed to seek") { /* retry with fresh file handle */ }

When it happens

Trigger: f.Seek(0, io.SeekEnd) returning an error — typically when the 'file' is a pipe/FIFO, has been truncated concurrently, or is on a filesystem returning EIO.

Common situations: frame.filename pointing at a FIFO or special file; concurrent truncation; failing disk/NFS mount.

Related errors

• Failed to open image data output file: %s with error: %w
• Failed to read data from image output data file: %w
• Failed to create a SHM file for transmission: %w
• Failed to convert image data output file: %s to absolute pat
• Failed to write image data to temp file for transmission: %w

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/d2bf4157cfba14ac. Report an issue: GitHub.