diff --git a/src/Lib/IO.php b/src/Lib/IO.php
index 09ba36c..47d1641 100644
--- a/src/Lib/IO.php
+++ b/src/Lib/IO.php
@@ -9,6 +9,7 @@ namespace MadLisp\Lib;
 
 use MadLisp\CoreFunc;
 use MadLisp\Env;
+use MadLisp\Vector;
 
 class IO implements ILib
 {
@@ -25,10 +26,82 @@ class IO implements ILib
             fn (string $dir) => chdir($dir)
         ));
 
-        $env->set('file?', new CoreFunc('file?', 'Check if file exists.', 1, 1,
+        $env->set('file?', new CoreFunc('file?', 'Check if file (or directory) exists.', 1, 1,
             fn (string $filename) => file_exists($filename)
         ));
 
+        $env->set('dir?', new CoreFunc('dir?', 'Check if directory exists and is not a file.', 1, 1,
+            fn (string $dir) => is_dir($dir)
+        ));
+
+        $env->set('fsize', new CoreFunc('fsize', 'Return the size of a file.', 1, 1,
+            fn (string $file) => @filesize($file)
+        ));
+
+        $env->set('ftime', new CoreFunc('ftime', 'Return the last modification time of a file.', 1, 1,
+            fn (string $file) => @filemtime($file)
+        ));
+
+        $env->set('ftouch', new CoreFunc('ftouch', 'Set the modification time of a file to the given value.', 1, 2,
+            fn (string $file, ?int $time = null) => @touch($file, $time !== null ? $time : time())
+        ));
+
+        $env->set('fperms', new CoreFunc('fperms', 'Get the permissions of a file. Permission bits are 1=execute, 2=write, 4=read.', 1, 1,
+            function (string $file) {
+                $perms = @fileperms($file);
+
+                if ($perms === false) {
+                    return null;
+                } else {
+                    return substr(sprintf('%o', $perms), -4);
+                }
+            }
+        ));
+
+        $env->set('fmod', new CoreFunc('fmod', 'Set the permissions of a file. Permission bits are 1=execute, 2=write, 4=read.', 2, 2,
+            fn (string $file, string $perms) => @chmod($file, octdec($perms))
+        ));
+
+        $env->set('fown', new CoreFunc('fown', 'Get the owner of a file. Give second argument as true to get the user ID.', 1, 2,
+            function (string $file, bool $rawId = false) {
+                $id = @fileowner($file);
+
+                if ($id === false) {
+                    return null;
+                } elseif ($rawId) {
+                    return $id;
+                } else {
+                    $info = posix_getpwuid($id);
+                    return $info['name'];
+                }
+            }
+        ));
+
+        $env->set('fgrp', new CoreFunc('fgrp', 'Get the group of a file. Give second argument as true to get the group ID.', 1, 2,
+            function (string $file, bool $rawId = false) {
+                $id = @filegroup($file);
+
+                if ($id === false) {
+                    return null;
+                } elseif ($rawId) {
+                    return $id;
+                } else {
+                    $info = posix_getgrgid($id);
+                    return $info['name'];
+                }
+            }
+        ));
+
+        $env->set('fcache', new CoreFunc('fcache', 'Clear the cache of file information.', 0, 0,
+            fn () => clearstatcache()
+        ));
+
+        $env->set('fdel', new CoreFunc('fdel', 'Delete a file.', 1, 1,
+            fn (string $file) => @unlink($file)
+        ));
+
+        // Simple read/write using file_get_contents and file_put_contents
+
         $env->set('fget', new CoreFunc('fget', 'Read contents of a file.', 1, 1,
             function (string $filename) {
                 return @file_get_contents($filename);
@@ -48,6 +121,8 @@ class IO implements ILib
             }
         ));
 
+        // Functions for working with file descriptors
+
         $env->set('fopen', new CoreFunc('fopen', 'Open a file for reading or writing. Give mode as second argument.', 2, 2,
             fn ($file, $mode) => @fopen($file, $mode)
         ));
@@ -72,6 +147,32 @@ class IO implements ILib
             fn ($handle) => @feof($handle)
         ));
 
+        // Functions for listing files
+
+        $env->set('glob', new CoreFunc('glob', 'Search for files and directories that match a pattern.', 1, 1,
+            function (string $pattern) {
+                $result = @glob($pattern);
+
+                if ($result === false) {
+                    return null;
+                } else {
+                    return new Vector($result);
+                }
+            }
+        ));
+
+        $env->set('read-dir', new CoreFunc('read-dir', 'Read the contents of a directory.', 1, 1,
+            function (string $dir) {
+                $result = @scandir($dir);
+
+                if ($result === false) {
+                    return null;
+                } else {
+                    return new Vector($result);
+                }
+            }
+        ));
+
         // Readline support
         if (extension_loaded('readline')) {
             $env->set('readline', new CoreFunc('readline', 'Read line of user input.', 0, 1,