Created Run nim source files like scripts (with tcc and binfmt_misc) (markdown)

Run-nim-source-files-like-scripts-(with-tcc-and-binfmt_misc).md

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+This is a rough guide on how to make nim source files behave like scripts.  This document targets debian/ubuntu-likes; you may have to adjust for other systems.
+
+## Prequisites
+* Install tcc (optional, but recommended): `sudo apt install tcc`
+* Make sure binfmt_misc support is available: `ls /proc/sys/fs/binfmt_misc/register`
+
+## The script runner
+
+Create `/usr/local/bin/nimtcc`, like so:
+
+```bash
+#!/bin/bash
+
+if [[ "$#" -eq 0 ]]; then
+	echo "at least 1 argument required" >&2
+	exit 1
+fi
+
+if [[ ! -e "$1" ]]; then
+	echo "not found: $1" >&2
+	exit 1
+fi
+
+umask u+rwx
+out=$(mktemp ${TMPDIR:-/tmp/}$(basename $1).XXXXXXXXXXXX)
+
+function finish() {
+	rm -- "$out"
+}
+trap finish EXIT
+
+nim compile \
+	--verbosity:0 \
+	'--hint[Processing]:off' \
+	--cc:tcc \
+	"-o:$out" \
+	-r $@
+```
+
+The script creates a temp file (in /tmp) to write the compiled program to, and immediately removes it thereafter again.
+
+* Make sure nim is available on PATH, or change the path to the binary in the script.
+* Mark it as executable: `sudo chmod +x /usr/local/bin/nimtcc`
+* .. and test it: `$ nimtcc my_script.nim`. If it doesn't work, fix it.
+
+**N.B.:**
+- This still creates a `nimcache` in the current directory.  I've left it in as a compromise to speed up iterative script development.  If this is not desired, you will have to adjust the script to create an additional directory (with mktemp -d), pass that to the compiler; and then remove it afterwards.
+- Similarily, you can get rid of the whole mktemp to write the script binary to the current directory.
+
+## binfmt_misc
+
+Now, optionally, make it so you can mark scripts as executable and run them directly. This requires binfmt_misc support in your kernel. Most modern kernels have this enabled by default.
+
+* `$ echo ':nimtcc:E::nim::/usr/local/bin/nimtcc:' | sudo tee -a /proc/sys/fs/binfmt_misc/register`
+* `$ chmod +x my_script.nim`
+* `$ ./my_script.nim`