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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "0b397cbb-8db3-40d9-a0a9-27ba0a774021",
+   "metadata": {},
+   "source": [
+    "## Automatically creating new binhost directories when profile or gcc version changes"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "97c6e8be-a571-4fea-84c4-b226f03f56c6",
+   "metadata": {},
+   "source": [
+    "On Gentoo Linux packages are compiled which is a time and energy consuming.\n",
+    "To minimise both, I have a binhost to share compiled binaries between devices.\n",
+    "The issues occurs when gcc major version changes - or a profile bump happens.\n",
+    "If I do not notice either - problem. Binaries might not be compatible.\n",
+    "So I wanted to automate a process of detection of those changes and automatically create subfolder for new binaries.\n",
+    "When investigating I learned a neat trick. For the wise ones this is trivial, for me it was enligtening.\n",
+    "Here it comes."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "2a688afd-5f24-4eab-a1c7-119d372367b5",
+   "metadata": {},
+   "source": [
+    "On a regular system, emerge resides here:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b1098db8-2f77-4b56-acef-f58113107dad",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "$ which emerge\n",
+    "/usr/bin/emerge"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "9a1dcd6c-3f8c-455f-9d56-21e5157d0846",
+   "metadata": {},
+   "source": [
+    "On my box with binhost:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "bcb9918c-20fb-49fd-baaf-b3b63356de5a",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "$ which emerge\n",
+    "/usr/local/bin/emerge"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "a84cf35c-e744-47c9-9500-d9b8c7d3bfef",
+   "metadata": {},
+   "source": [
+    "And here is $PATH:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "94092561-ae6b-41eb-831a-71bffcf30e6e",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "$ echo $PATH\n",
+    "/usr/local/sbin:/usr/local/bin:/usr/bin:/opt/bin:/usr/lib/llvm/18/bin:/usr/lib/llvm/17/bin"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "eb05de7d-f2f3-4cd3-acc2-769e096a3a5b",
+   "metadata": {},
+   "source": [
+    "So we see that on binhost box, there is emerge that resides in location preceeding regular emerge - so it gets called first.\n",
+    "It contains a shell script as follows:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b9f78265-a1de-47eb-be21-bb66c1ed3bed",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "#!/usr/bin/env bash\n",
+    "#\n",
+    "# Script checking that binhost path exists before running emerge and\n",
+    "# creating it if not exists\n",
+    "\n",
+    "PROFILE=$(eselect profile show|sed -n 2p|cut -d '/' -f4)\n",
+    "GCC_VERSION=$(eselect gcc show|cut -d '-' -f5)\n",
+    "BINHOST_DIR=\"/var/cache/binpkgs/${PROFILE}/gcc-${GCC_VERSION}.x/armv8a\"\n",
+    "\n",
+    "if [ ! -d \"${BINHOST_DIR}\" ]; then\n",
+    "        echo \"${BINHOST_DIR} does not exist, creating\"\n",
+    "        mkdir -p \"${BINHOST_DIR}\"\n",
+    "else echo \"Binhost directory ${BINHOST_DIR} exists, proceeding with emerge ...\"\n",
+    "fi\n",
+    "\n",
+    "PKGDIR=\"${BINHOST_DIR}\" /usr/bin/emerge \"$@\""
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d6d085ea-b68f-4220-adaf-00223393e58e",
+   "metadata": {},
+   "source": [
+    "So on every profile change subfolder to /var/cache/binpkgs gets created,\n",
+    "on every gcc major version change, subfolder to /var/cache/binpkgs/<profile> gets created.\n",
+    "If folder already exists script only prints a message.\n",
+    "Then it calls /usr/bin/emerge - the regular emerge - with $PKGDIR variable, so binary packages are saved to the correct directory. "
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "1d464645-b7ac-4cbc-b5cc-1bd4bd976f06",
+   "metadata": {},
+   "source": [
+    "This is structure of /var/cache/binpkgs:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "dee2b348-d16d-4709-a7cd-ac9424934009",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "$ tree -L 3 /var/cache/binpkgs/\n",
+    "/var/cache/binpkgs/\n",
+    "├── 17.0\n",
+    "│   └── gcc-13.x\n",
+    "│       └── armv8a\n",
+    "└── 23.0\n",
+    "    ├── gcc-13.x\n",
+    "    │   └── armv8a\n",
+    "    └── gcc-14.x\n",
+    "        └── armv8a"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "9f8f4a71-9fd1-4678-9cb0-a580c94f4582",
+   "metadata": {},
+   "source": [
+    "One less thing to worry about."
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.7"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}