add library.sh with retry function

flake.nix

@@ -36,35 +36,60 @@
         '';
     in
     {
-      packages.${system} = lib.attrsets.listToAttrs (map
-        (a@{ name, ... }: lib.attrsets.nameValuePair name (makeTestProgram a))
-        [
-          {
-            name = "query-minimum-services";
-            script = ./query-services-state.sh;
-            env-vars = [{
-              name = "EXPECTED_RESPONSE_FILE";
-              value = ./minimal-services-expected-response.json;
-            }];
-          }
-          {
-            name = "query-all-services";
-            script = ./query-services-state.sh;
-            env-vars = [{
-              name = "EXPECTED_RESPONSE_FILE";
-              value = ./all-services-expected-response.json;
-            }];
-          }
-          {
-            name = "enable-service";
-            script = ./enable-service.sh;
-            env-vars = [ ];
-          }
-          {
-            name = "nixos-rebuild";
-            script = ./nixos-rebuild.sh;
-            env-vars = [ ];
-          }
-        ]);
+      packages.${system} = lib.attrsets.listToAttrs
+        (
+          (map
+            (a@{ name, ... }: lib.attrsets.nameValuePair name (makeTestProgram a))
+            [
+              {
+                name = "query-minimum-services";
+                script = ./query-services-state.sh;
+                env-vars = [{
+                  name = "EXPECTED_RESPONSE_FILE";
+                  value = ./minimal-services-expected-response.json;
+                }];
+              }
+              {
+                name = "query-all-services";
+                script = ./query-services-state.sh;
+                env-vars = [{
+                  name = "EXPECTED_RESPONSE_FILE";
+                  value = ./all-services-expected-response.json;
+                }];
+              }
+              {
+                name = "enable-service";
+                script = ./enable-service.sh;
+                env-vars = [ ];
+              }
+              {
+                name = "nixos-rebuild";
+                script = ./nixos-rebuild.sh;
+                env-vars = [ ];
+              }
+            ]
+          )
+          ++ [
+            {
+              name = "library";
+              value =
+                builtins.filterSource (p: _t: baseNameOf p == "library.sh") ./.;
+            }
+          ]
+        );
+      devShells.${system}.default = pkgs.mkShell
+        {
+          packages = with pkgs;
+            [
+              curl
+              diffutils
+              gzip
+              jd-diff-patch
+              jq
+              openssh
+              gnutar
+              iputils
+            ];
+        };
     };
 }

library.sh

@@ -0,0 +1,16 @@
+retry() {
+    local t0 cur_date remaining
+    local timeout="${1:?error: no timeout given}"
+    local period="${2:?error: no period given}"
+    declare -a cmd=("${@:3}")
+
+    t0="$(date '+%s')"
+    until "${cmd[@]}"
+    do
+        sleep "$period"
+        cur_date="$(date '+%s')"
+        remaining=$((t0 + timeout - cur_date))
+        [ "$remaining" -gt 0 ] || return 1
+        echo "$remaining seconds remain before teardown"
+    done
+}