From b1bcd7acba553608e44cd4e3d11b92d792d520d3 Mon Sep 17 00:00:00 2001
From: Gabriella Gonzalez <GenuineGabriella@gmail.com>
Date: Sat, 29 Mar 2025 18:05:23 -0700
Subject: [PATCH] nixos/bash: Add support for `/etc/bash_logout`
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This adds a new `programs.bash.logout` option which configures the Bash
logout script.

Carefully note that the stock Bash does not support a global logout
script and only supports user-local logout scripts in `~/.bash_logout`.
However, Nixpkgs patches Bash to support a global `/etc/bash_logout`
script here:

https://github.com/NixOS/nixpkgs/blob/ee0fecd318d77921ecb0f536df98db184a08305d/pkgs/shells/bash/5.nix#L48

… and the `programs.bash.logout` option configures that logout script.
---
 nixos/modules/programs/bash/bash.nix | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/nixos/modules/programs/bash/bash.nix b/nixos/modules/programs/bash/bash.nix
index 213f0d2698ae..6acbea562822 100644
--- a/nixos/modules/programs/bash/bash.nix
+++ b/nixos/modules/programs/bash/bash.nix
@@ -111,6 +111,13 @@ in
         internal = true;
       };
 
+      logout = lib.mkOption {
+        default = "";
+        description = ''
+          Shell script code called during login bash shell logout.
+        '';
+        type = lib.types.lines;
+      };
     };
 
   };
@@ -197,6 +204,21 @@ in
         fi
       '';
 
+      environment.etc.bash_logout.text = ''
+        # /etc/bash_logout: DO NOT EDIT -- this file has been generated automatically.
+
+        # Only execute this file once per shell.
+        if [ -n "$__ETC_BASHLOGOUT_SOURCED" ] || [ -n "$NOSYSBASHLOGOUT" ]; then return; fi
+        __ETC_BASHLOGOUT_SOURCED=1
+
+        ${cfg.logout}
+
+        # Read system-wide modifications.
+        if test -f /etc/bash_logout.local; then
+            . /etc/bash_logout.local
+        fi
+      '';
+
       # Configuration for readline in bash. We use "option default"
       # priority to allow user override using both .text and .source.
       environment.etc.inputrc.source = lib.mkOptionDefault ./inputrc;