diff --git a/src/cli/cli.odin b/src/cli/cli.odin
index 86f811a..8e2d1f7 100644
--- a/src/cli/cli.odin
+++ b/src/cli/cli.odin
@@ -3,6 +3,7 @@ package cli
 import "core:flags"
 import "core:fmt"
 import "core:os"
+import "core:strings"
 
 Options :: struct {
 	verbose:     bool `args:"name=verbose"                    usage:"Enable verbose output"`,
@@ -13,7 +14,7 @@ Options :: struct {
 	// overflow:    [dynamic]string,
 }
 
-parse :: proc() -> Options {
+parse :: proc(working_dir: string) -> Options {
 	opts: Options
 
 	err := flags.parse(&opts, os.args[1:], .Unix)
@@ -23,16 +24,48 @@ parse :: proc() -> Options {
 		os.exit(1)
 	}
 
-	if opts.compression > 12 {
-		err := flags.Validation_Error {
-			message = fmt.tprintf(
-				`Invalid compression "%d". Compression higher than allowed maximum.`,
-				opts.compression,
-			),
-		}
-		flags.print_errors(typeid_of(Options), err, os.args[0], .Unix)
-		os.exit(1)
-	}
+	verify(opts, working_dir)
 
 	return opts
 }
+
+@(private)
+verify :: proc(opts: Options, working_dir: string) {
+	if opts.compression > 12 {
+		throw_error(
+			`Invalid compression "%d". Compression higher than allowed maximum.`,
+			opts.compression,
+		)
+	}
+
+	input_path := os.name(opts.input)
+	if !os.is_dir(input_path) {
+		throw_error(`Invalid input "%v". Should be a directory`, input_path)
+	}
+
+	if opts.output != nil {
+		output_path := os.name(opts.output)
+		if !os.is_dir(output_path) {
+			throw_error(
+				`Invalid output "%v". Should be a directory`,
+				output_path,
+			)
+		}
+	}
+
+	if !strings.has_prefix(input_path, working_dir) {
+		throw_error(
+			`Invalid input "%v". Should be a subdirectory of the working directory.`,
+			input_path,
+		)
+	}
+}
+
+@(private)
+throw_error :: proc(fmt_str: string, args: ..any) {
+	err := flags.Validation_Error {
+		message = fmt.tprintf(fmt_str, ..args),
+	}
+	flags.print_errors(typeid_of(Options), err, os.args[0], .Unix)
+	os.exit(1)
+}
diff --git a/src/file/file.odin b/src/file/file.odin
index c1b5dc6..6858b52 100644
--- a/src/file/file.odin
+++ b/src/file/file.odin
@@ -1,7 +1,28 @@
 package file
 
+import "core:fmt"
+import "core:os"
+
 // TODO:
 // - list files in directory
 //   - get relative path
 // - read file contents
 // - write file contents
+
+working_dir: string
+
+store_working_dir :: proc(allocator := context.allocator) {
+	wd, err := os.get_working_directory(allocator)
+	if err != nil {
+		fmt.eprintln("error: get working directory failed:", err)
+		os.exit(1)
+	}
+	working_dir = wd
+}
+
+remove_working_dir :: proc() {
+	if working_dir != "" {
+		delete(working_dir)
+		working_dir = ""
+	}
+}
diff --git a/src/file/list_dir.odin b/src/file/list_dir.odin
index be676d3..bee1539 100644
--- a/src/file/list_dir.odin
+++ b/src/file/list_dir.odin
@@ -34,20 +34,13 @@ list_dir_recursive_by_path :: proc(
 @(private)
 list_dir_recursive_by_path_impl :: proc(
 	path: string,
-	allocator: runtime.Allocator
+	allocator: runtime.Allocator,
 ) -> [dynamic]DirectoryEntry {
 	if !os.is_dir(path) {
 		fmt.eprintln("error: path is not a directory:", path)
 		os.exit(1)
 	}
 
-	working_dir, wd_err := os.get_working_directory(allocator)
-	if wd_err != nil {
-		fmt.eprintln("error: get working directory failed:", wd_err)
-		os.exit(1)
-	}
-	defer delete(working_dir, allocator)
-
 	result := make([dynamic]DirectoryEntry, allocator)
 
 	queue := make([dynamic]string, 0, 1, allocator) // reserve 1 slot
diff --git a/src/main.odin b/src/main.odin
index 4086c10..2818f1f 100644
--- a/src/main.odin
+++ b/src/main.odin
@@ -8,7 +8,10 @@ import "src:file"
 VERSION :: #config(VERSION, "dev")
 
 main :: proc() {
-	opts := cli.parse()
+	file.store_working_dir()
+	defer file.remove_working_dir()
+
+	opts := cli.parse(file.working_dir)
 
 	fmt.println("verbose:", opts.verbose)
 	fmt.println("compression:", opts.compression)