diff --git a/lib/index.js b/lib/index.js
index 3a2345a..12f3b5e 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -430,8 +430,8 @@ function main() {
         const files = [
             {
                 name: core.getInput("name"),
-                contents: core.getInput("key", {
-                    required: true,
+                contents: insertLf(core.getInput("key", { required: true }), {
+                    append: true,
                 }),
                 options: {
                     mode: 0o400,
@@ -440,9 +440,10 @@ function main() {
             },
             {
                 name: "known_hosts",
-                contents: insertLf(core.getInput("known_hosts", {
-                    required: true,
-                })),
+                contents: insertLf(core.getInput("known_hosts", { required: true }), {
+                    prepend: true,
+                    append: true,
+                }),
                 options: {
                     mode: 0o644,
                     flag: "a",
@@ -450,7 +451,10 @@ function main() {
             },
             {
                 name: "config",
-                contents: insertLf(core.getInput("config")),
+                contents: insertLf(core.getInput("config"), {
+                    prepend: true,
+                    append: true,
+                }),
                 options: {
                     mode: 0o644,
                     flag: "a",
@@ -505,19 +509,21 @@ function getHomeEnv() {
 }
 /**
  * prepend/append LF to value if not empty
- * @param value the value to prepend LF
- * @returns prepended value
+ * @param value the value to insert LF
+ * @param options options
+ * @returns new value
  */
-function insertLf(value) {
+function insertLf(value, options) {
+    const normalizedOptions = Object.assign({ prepend: false, append: false }, options);
     let affectedValue = value;
     if (value.length === 0) {
         // do nothing if empty
         return "";
     }
-    if (!affectedValue.startsWith("\n")) {
+    if (normalizedOptions.prepend && !affectedValue.startsWith("\n")) {
         affectedValue = `\n${affectedValue}`;
     }
-    if (!affectedValue.endsWith("\n")) {
+    if (normalizedOptions.append && !affectedValue.endsWith("\n")) {
         affectedValue = `${affectedValue}\n`;
     }
     return affectedValue;
diff --git a/src/main.ts b/src/main.ts
index 73b704a..97c78e8 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -10,6 +10,13 @@ interface FileInfo
 	options: fs.WriteFileOptions;
 }
 
+/** options for insertLf() */
+interface InsertLfOptions
+{
+	prepend?: boolean;
+	append?: boolean;
+}
+
 /**
  * main function
  */
@@ -20,9 +27,9 @@ function main(): void
 		const files: FileInfo[] = [
 			{
 				name: core.getInput("name"),
-				contents: insertLfToEnd(core.getInput("key", {
-					required: true,
-				})),
+				contents: insertLf(core.getInput("key", {required: true}), {
+					append: true,
+				}),
 				options: {
 					mode: 0o400,
 					flag: "ax",
@@ -30,9 +37,10 @@ function main(): void
 			},
 			{
 				name: "known_hosts",
-				contents: insertLf(core.getInput("known_hosts", {
-					required: true,
-				})),
+				contents: insertLf(core.getInput("known_hosts", {required: true}), {
+					prepend: true,
+					append: true,
+				}),
 				options: {
 					mode: 0o644,
 					flag: "a",
@@ -40,7 +48,10 @@ function main(): void
 			},
 			{
 				name: "config",
-				contents: insertLf(core.getInput("config")),
+				contents: insertLf(core.getInput("config"), {
+					prepend: true,
+					append: true,
+				}),
 				options: {
 					mode: 0o644,
 					flag: "a",
@@ -110,12 +121,18 @@ function getHomeEnv(): string
 }
 
 /**
- * append LF to value to the end if not empty
- * @param value the value to prepend LF
- * @returns prepended value
+ * prepend/append LF to value if not empty
+ * @param value the value to insert LF
+ * @param options options
+ * @returns new value
  */
-function insertLfToEnd(value: string): string
+function insertLf(value: string, options: InsertLfOptions): string
 {
+	const normalizedOptions: Required<InsertLfOptions> = {
+		prepend: false,
+		append: false,
+		...options,
+	};
 	let affectedValue = value;
 
 	if(value.length === 0)
@@ -123,7 +140,11 @@ function insertLfToEnd(value: string): string
 		// do nothing if empty
 		return "";
 	}
-	if(!affectedValue.endsWith("\n"))
+	if(normalizedOptions.prepend && !affectedValue.startsWith("\n"))
+	{
+		affectedValue = `\n${affectedValue}`;
+	}
+	if(normalizedOptions.append && !affectedValue.endsWith("\n"))
 	{
 		affectedValue = `${affectedValue}\n`;
 	}
@@ -131,27 +152,4 @@ function insertLfToEnd(value: string): string
 	return affectedValue;
 }
 
-/**
- * prepend/append LF to value if not empty
- * @param value the value to prepend LF
- * @returns prepended value
- */
-function insertLf(value: string): string
-{
-	let affectedValue = value;
-
-	if(value.length === 0)
-	{
-		// do nothing if empty
-		return "";
-	}
-	if(!affectedValue.startsWith("\n"))
-	{
-		affectedValue = `\n${affectedValue}`;
-	}
-	affectedValue = insertLfToEnd(affectedValue);
-
-	return affectedValue;
-}
-
 main();