Don't want to wait for computations (e.g. checksums) on large files after they are downloaded? Do the computation during the download!

catdld.sh

#!/bin/bash
# No warranty is provided!
# 
# Rather hacky script for streaming downloaded files through pipe.
# Requires inotify-tools package installed.
# It does not handle some failures properly!
# 
# Assumes that a browser saves the temporary result into the .part file and the browser is the only process that opens the file for writing.
# 
# How it works: The script streams the content of the .part file to stdout. When the .part file is closed, it stops streaming.
#
# Note that I am not sure if there is a race condition that could stop the streaming prematurely in some cases. Some simple experiments suggest that it can't happen, but I am not 100% sure.
# 
# Example of usage: catdld some-large-file-being-downloaded | sha256sum
# This will compute the sha256 of a large file in the background while the file is being downloaded, so you don't have to wait for checking the checksum after download. Because the CPU is much faster than the network, the checksum is available virtually immediately after the download. It may also save disk reads thanks to caches.

FILE="$1"
PART="$FILE.part"

inotifywait -e close_write "$PART" > /dev/null&
watchpid="$!"

tail -f -c +0 --pid="$watchpid" "$PART" || exit 1