kovidgoyal/kitty · error

Failed to create a temp file for image data transmission: %w

Error message

Failed to create a temp file for image data transmission: %w

What it means

For in-memory frames sent by file transmission, icat writes the bytes to a RAM-backed temp file (images.CreateTempInRAM); creating that temp file failed.

Source

Thrown at kittens/icat/transmit.go:137

	err = gc.WriteWithPayloadTo(os.Stdout, utils.UnsafeStringToBytes(mmap.Name()))
	return
}

func transmit_file(imgd *image_data, frame_num int, frame *image_frame) (err error) {
	is_temp := false
	fname := ""
	var data_size int
	if frame.in_memory_bytes == nil {
		fname, err = filepath.Abs(frame.filename)
		if err != nil {
			return fmt.Errorf("Failed to convert image data output file: %s to absolute path with error: %w", frame.filename, err)
		}
		frame.filename = "" // so it isn't deleted in cleanup
	} else {
		is_temp = true
		f, err := images.CreateTempInRAM()
		if err != nil {
			return fmt.Errorf("Failed to create a temp file for image data transmission: %w", err)
		}
		data_size = len(frame.in_memory_bytes)
		_, err = bytes.NewBuffer(frame.in_memory_bytes).WriteTo(f)
		f.Close()
		if err != nil {
			os.Remove(f.Name())
			return fmt.Errorf("Failed to write image data to temp file for transmission: %w", err)
		}
		fname = f.Name()
	}
	gc := gc_for_image(imgd, frame_num, frame)
	gc.SetTransmission(utils.IfElse(is_temp, graphics.GRT_transmission_tempfile, graphics.GRT_transmission_file))
	if data_size > 0 {
		gc.SetDataSize(uint64(data_size))
	}
	return gc.WriteWithPayloadTo(os.Stdout, utils.UnsafeStringToBytes(fname))
}

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Free space in the tmpfs/TMPDIR used for temp files or enlarge it
2. Set TMPDIR to a location with adequate space
3. Reduce image sizes; close other processes hogging fds/space

Example fix

# before
docker run ... kitten icat big.png
# after
docker run -e TMPDIR=/var/tmp ... kitten icat big.png

var s syscall.Statfs_t
syscall.Statfs(os.TempDir(), &s)
if s.Bavail*uint64(s.Bsize) < uint64(imgSize) { /* free space or set bigger TMPDIR */ }

if err != nil && strings.Contains(err.Error(), "temp file") { /* free tmpfs or point TMPDIR elsewhere and retry */ }

When it happens

Trigger: CreateTempInRAM failing — tmpfs (e.g. /dev/shm or TMPDIR pointing at tmpfs) full or unwritable, or too many temp files.

Common situations: Small /dev/shm in containers with large images; TMPDIR set to a full/unwritable location; file-descriptor exhaustion.

Related errors

• Failed to write image data to temp file for transmission: %w
• Timed out waiting for a response from the terminal: %w
• Invalid value for --background: %w
• Invalid value for --z-index with error: %w
• unknown fit specification: %#v

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/dbc9ece1decc5735. Report an issue: GitHub.