kovidgoyal/kitty · error

Failed to write image data to temp file for transmission: %w

Error message

Failed to write image data to temp file for transmission: %w

What it means

Raised by transmit_file in the icat kitten when image data held in memory cannot be written to a temporary file before being transmitted to the terminal. The temp file is used when the image frame exists only as in-memory bytes rather than a file on disk. The error wraps the underlying os write failure.

Source

Thrown at kittens/icat/transmit.go:144

	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))
}

func transmit_stream(imgd *image_data, frame_num int, frame *image_frame) (err error) {
	data := frame.in_memory_bytes
	if data == nil {
		data, err = os.ReadFile(frame.filename)
		if err != nil {
			return fmt.Errorf("Failed to read image data output file: %s with error: %w", frame.filename, err)
		}

View on GitHub (pinned to 6d5d0c4406)

Solutions

1. Check TMPDIR / temp directory writability: echo test > $TMPDIR/x and remove it
2. Free disk space or point TMPDIR to a writable location with space
3. If running in a container/sandbox, mount a writable /tmp
4. Retry after fixing permissions on the temp dir

Example fix

# before
TMPDIR=/nonexistent kitty +kitten icat img.png
# after
mkdir -p /tmp/kitty && TMPDIR=/tmp/kitty kitty +kitten icat img.png

import "os"

tmp := os.TempDir()
f, err := os.CreateTemp(tmp, "probe")
if err != nil { /* fail early with a clear message */ }
f.Close(); os.Remove(f.Name())

When it happens

Trigger: Calling the icat kitten with an image supplied via stdin or an in-memory frame (e.g. from a pipe or processed image) when the temp directory is not writable or the disk is full. bytes.NewBuffer(...).WriteTo(f) fails mid-write.

Common situations: TMPDIR pointing to a nonexistent or read-only directory, disk-full on /tmp, sandboxed/container environments with a read-only temp dir, or permissions issues on the kitty config/temp paths.

Related errors

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

AI-assisted analysis of kovidgoyal/kitty@6d5d0c4406 (2026-08-27). Data as JSON: /api/errors/b003e351f25012ca. Report an issue: GitHub.