Use Nix function to perform replacement

build/builder.sh

@@ -5,7 +5,7 @@ cp -r $src/* .
 
 # Hugo can't set baseUrl via CLI for multi-lingual hosts.
 # We have to manually edit the configuration.
-sed -i "$urlSub" config.toml
+patchPhase
 
 # Build site with Hugo
 hugo $extraFlags

flake.lock

@@ -3,11 +3,11 @@
     "blog-source": {
       "flake": false,
       "locked": {
-        "lastModified": 1649577215,
-        "narHash": "sha256-8TqSSEoRwlqCbBpombBCPDlzbiF9OPopdx0o4spFbAU=",
+        "lastModified": 1651357493,
+        "narHash": "sha256-F5llZ7YygjVZTkDQ3jOMrqnEFZ8zfK9z3hniEtguyG0=",
         "ref": "master",
-        "rev": "fe1c05fe46336ab43402c863dbba49851cd63c08",
-        "revCount": 567,
+        "rev": "2474804258bc892a7d0ba53745ac25fea878a5a6",
+        "revCount": 578,
         "submodules": true,
         "type": "git",
         "url": "https://dev.danilafe.com/Web-Projects/blog-static.git"

lib.nix

@@ -7,11 +7,9 @@ let
     inherit (settings) src ssl host;
     name = "blog-static";
     version = settings.src.rev;
-    urlSub =
-      let
-        regexEscape = lib.escape [ "/" "(" ")" "[" "]" "+" "*" "\\" ];
-      in
-        with settings.replaceUrl; "s/${regexEscape from}/${regexEscape to}/g";
+    postPatch = with settings.replaceUrl; ''
+      substituteInPlace config.toml --replace ${from} ${to}
+    '';
     publicPath = settings.path;
     extraFlags = (if settings.drafts then " -D " else "") + settings.extraFlags;
     builder = ./build/builder.sh;