2 files changed, 72 insertions, 0 deletions
diff --git a/src/zencore/filesystem.cpp b/src/zencore/filesystem.cpp
index a63594be9..00ee4f45c 100644
--- a/src/zencore/filesystem.cpp
+++ b/src/zencore/filesystem.cpp
@@ -2963,6 +2963,35 @@ GetEnvVariable(std::string_view VariableName)
 	return "";
 }
 
+std::string
+ExpandEnvironmentVariables(std::string_view Input)
+{
+	std::string Result;
+	Result.reserve(Input.size());
+
+	for (size_t i = 0; i < Input.size(); ++i)
+	{
+		if (Input[i] == '%')
+		{
+			size_t End = Input.find('%', i + 1);
+			if (End != std::string_view::npos && End > i + 1)
+			{
+				std::string_view VarName = Input.substr(i + 1, End - i - 1);
+				std::string		 Value	 = GetEnvVariable(VarName);
+				if (!Value.empty())
+				{
+					Result += Value;
+					i = End;
+					continue;
+				}
+			}
+		}
+		Result += Input[i];
+	}
+
+	return Result;
+}
+
 std::error_code
 RotateFiles(const std::filesystem::path& Filename, std::size_t MaxFiles)
 {
@@ -4108,6 +4137,45 @@ TEST_CASE("filesystem.MakeSafeAbsolutePath")
 #	endif	// ZEN_PLATFORM_WINDOWS
 }
 
+TEST_CASE("ExpandEnvironmentVariables")
+{
+	// No variables — pass-through
+	CHECK_EQ(ExpandEnvironmentVariables("plain/path"), "plain/path");
+	CHECK_EQ(ExpandEnvironmentVariables(""), "");
+
+	// Single percent sign is not a variable reference
+	CHECK_EQ(ExpandEnvironmentVariables("50%"), "50%");
+
+	// Empty variable name (%%) is not expanded
+	CHECK_EQ(ExpandEnvironmentVariables("%%"), "%%");
+
+	// Known variable
+#	if ZEN_PLATFORM_WINDOWS
+	// PATH is always set on Windows
+	std::string PathValue = GetEnvVariable("PATH");
+	CHECK(!PathValue.empty());
+	CHECK_EQ(ExpandEnvironmentVariables("%PATH%"), PathValue);
+	CHECK_EQ(ExpandEnvironmentVariables("prefix/%PATH%/suffix"), "prefix/" + PathValue + "/suffix");
+#	else
+	std::string HomeValue = GetEnvVariable("HOME");
+	CHECK(!HomeValue.empty());
+	CHECK_EQ(ExpandEnvironmentVariables("%HOME%"), HomeValue);
+	CHECK_EQ(ExpandEnvironmentVariables("prefix/%HOME%/suffix"), "prefix/" + HomeValue + "/suffix");
+#	endif
+
+	// Unknown variable is left unexpanded
+	CHECK_EQ(ExpandEnvironmentVariables("%ZEN_UNLIKELY_SET_VAR_12345%"), "%ZEN_UNLIKELY_SET_VAR_12345%");
+
+	// Multiple variables
+#	if ZEN_PLATFORM_WINDOWS
+	std::string OSValue = GetEnvVariable("OS");
+	if (!OSValue.empty())
+	{
+		CHECK_EQ(ExpandEnvironmentVariables("%PATH%/%OS%"), PathValue + "/" + OSValue);
+	}
+#	endif
+}
+
 TEST_SUITE_END();
 
 #endif
diff --git a/src/zencore/include/zencore/filesystem.h b/src/zencore/include/zencore/filesystem.h
index 6dc159a83..73769cdb4 100644
--- a/src/zencore/include/zencore/filesystem.h
+++ b/src/zencore/include/zencore/filesystem.h
@@ -400,6 +400,10 @@ void GetDirectoryContent(const std::filesystem::path& RootDir,
 
 std::string GetEnvVariable(std::string_view VariableName);
 
+// Expands %VAR% environment variable references in a string.
+// Unknown or empty variables are left unexpanded.
+std::string ExpandEnvironmentVariables(std::string_view Input);
+
 std::filesystem::path SearchPathForExecutable(std::string_view ExecutableName);
 
 std::error_code RotateFiles(const std::filesystem::path& Filename, std::size_t MaxFiles);