feat: add rudimentary tab completion for executables to shell

programs/src/shell/tabcompletion.cpp

@@ -0,0 +1,74 @@
+/* 
+ * tabcompletion.cpp
+ * Tab completion module
+ * Copyright (c) 2026 Daniel Hammer
+ */ 
+
+#include <montauk/string.h>
+#include <montauk/syscall.h>
+
+#define RD_MAX 128
+
+/*
+	Does the file path end with .elf? 
+*/
+bool is_executable(const char* path) {
+	size_t len = montauk::slen(path);
+
+	if (path[len - 1] == 'f' &&
+		path[len - 2] == 'l' &&
+		path[len - 3] == 'e' && 
+		path[len - 4] == '.')
+	{
+		return true;
+	}
+
+	return false;
+}
+
+/*
+	i.e., "shell.elf" => "shell"
+*/
+const char* strip_elf_extension(const char* path) {
+	size_t len = montauk::slen(path);
+
+	char* p = (char* ) path;
+	p[len - 4] = '\0';
+
+	return (const char*)p;
+}
+
+int get_completions(		// returns no. of results 
+		char*	string, 	// String to match/complete
+		char**	array, 		// Array of strings containing completions
+		int	arrayMax
+	) {
+	
+	const char* names[RD_MAX] 	= { };
+
+	int n = montauk::readdir("0:/os", names, RD_MAX);
+	int r = 0;
+
+	for (int i = 0; i < n; i++) {
+		/*
+			Shift by 3 characters (names[i] + 3):
+				"os/shell.elf" => "shell.elf"
+
+			This is somewhat of a workaround. 
+		*/
+		if (montauk::starts_with(names[i] + 3, (const char*)string)) {
+			if (
+				r > arrayMax ||
+				!is_executable(names[i])
+			) break;
+
+			char* p = (char *)names[i] + 3;
+			strip_elf_extension(p);
+
+			array[r] = (char *)p;
+			r++;
+		} 
+	}
+
+	return r;
+}