Add env var support for home dir

packages/safe-chain/src/config/environmentVariables.js

@@ -55,3 +55,14 @@ export function getMinimumPackageAgeExclusions() {
 export function getMalwareListBaseUrl() {
   return process.env.SAFE_CHAIN_MALWARE_LIST_BASE_URL;
 }
+
+/**
+ * Gets the safe-chain base directory from environment variable.
+ * When set, all safe-chain data (bin, shims, scripts) will be placed under this directory
+ * instead of the default ~/.safe-chain, enabling system-wide installations.
+ * Example: "/usr/local/.safe-chain"
+ * @returns {string | undefined}
+ */
+export function getSafeChainDir() {
+  return process.env.SAFE_CHAIN_DIR;
+}

packages/safe-chain/src/config/environmentVariables.spec.js

@@ -0,0 +1,30 @@
+import { describe, it, beforeEach, afterEach } from "node:test";
+import assert from "node:assert";
+
+const { getSafeChainDir } = await import("./environmentVariables.js");
+
+describe("getSafeChainDir", () => {
+  let original;
+
+  beforeEach(() => {
+    original = process.env.SAFE_CHAIN_DIR;
+  });
+
+  afterEach(() => {
+    if (original !== undefined) {
+      process.env.SAFE_CHAIN_DIR = original;
+    } else {
+      delete process.env.SAFE_CHAIN_DIR;
+    }
+  });
+
+  it("returns undefined when SAFE_CHAIN_DIR is not set", () => {
+    delete process.env.SAFE_CHAIN_DIR;
+    assert.strictEqual(getSafeChainDir(), undefined);
+  });
+
+  it("returns the value of SAFE_CHAIN_DIR when set", () => {
+    process.env.SAFE_CHAIN_DIR = "/usr/local/.safe-chain";
+    assert.strictEqual(getSafeChainDir(), "/usr/local/.safe-chain");
+  });
+});