diff --git a/os/Makefile b/os/Makefile
index fb985e4..cb7abbd 100644
--- a/os/Makefile
+++ b/os/Makefile
@@ -44,7 +44,6 @@ $(KERNEL_BIN): kernel
 kernel:
 	@echo Platform: $(BOARD)
 	@cd ../user && make build
-	@cargo clean
 	@cargo build --release
 
 clean:
diff --git a/user/src/bin/initproc.rs b/user/src/bin/initproc.rs
index 75e79d9..7295013 100644
--- a/user/src/bin/initproc.rs
+++ b/user/src/bin/initproc.rs
@@ -13,9 +13,8 @@ use user::{
 
 #[no_mangle]
 fn main() -> i32 {
-    if fork() == 0 {
-        // child process
-        exec("user_shell\0");
+   if fork() == 0 {
+        exec("user_shell\0", &[0 as *const u8]);
     } else {
         loop {
             let mut exit_code: i32 = 0;
diff --git a/user/src/bin/user_shell.rs b/user/src/bin/user_shell.rs
index bb8a3fb..9c28988 100644
--- a/user/src/bin/user_shell.rs
+++ b/user/src/bin/user_shell.rs
@@ -12,12 +12,21 @@ const DL: u8 = 0x7fu8;
 const BS: u8 = 0x08u8;
 
 use alloc::string::String;
-use user::{fork, exec, waitpid};
+use alloc::vec::Vec;
+use user::{
+    fork,
+    exec,
+    waitpid,
+    open,
+    OpenFlags,
+    close,
+    dup,
+};
 use user::console::getchar;
 
 #[no_mangle]
 pub fn main() -> i32 {
-    println!("Rust user shell");
+     println!("Rust user shell");
     let mut line: String = String::new();
     print!(">> ");
     loop {
@@ -26,11 +35,78 @@ pub fn main() -> i32 {
             LF | CR => {
                 println!("");
                 if !line.is_empty() {
-                    line.push('\0');
+                    let args: Vec<_> = line.as_str().split(' ').collect();
+                    let mut args_copy: Vec<String> = args
+                    .iter()
+                    .map(|&arg| {
+                        let mut string = String::new();
+                        string.push_str(arg);
+                        string
+                    })
+                    .collect();
+
+                    args_copy
+                    .iter_mut()
+                    .for_each(|string| {
+                        string.push('\0');
+                    });
+
+                    // redirect input
+                    let mut input = String::new();
+                    if let Some((idx, _)) = args_copy
+                    .iter()
+                    .enumerate()
+                    .find(|(_, arg)| arg.as_str() == "<\0") {
+                        input = args_copy[idx + 1].clone();
+                        args_copy.drain(idx..=idx + 1);
+                    }
+
+                    // redirect output
+                    let mut output = String::new();
+                    if let Some((idx, _)) = args_copy
+                    .iter()
+                    .enumerate()
+                    .find(|(_, arg)| arg.as_str() == ">\0") {
+                        output = args_copy[idx + 1].clone();
+                        args_copy.drain(idx..=idx + 1);
+                    }
+
+                    let mut args_addr: Vec<*const u8> = args_copy
+                        .iter()
+                        .map(|arg| arg.as_ptr())
+                        .collect();
+                    args_addr.push(0 as *const u8);
                     let pid = fork();
                     if pid == 0 {
+                        // input redirection
+                        if !input.is_empty() {
+                            let input_fd = open(input.as_str(), OpenFlags::RDONLY);
+                            if input_fd == -1 {
+                                println!("Error when opening file {}", input);
+                                return -4;
+                            }
+                            let input_fd = input_fd as usize;
+                            close(0);
+                            assert_eq!(dup(input_fd), 0);
+                            close(input_fd);
+                        }
+                        // output redirection
+                        if !output.is_empty() {
+                            let output_fd = open(
+                                output.as_str(),
+                                OpenFlags::CREATE | OpenFlags::WRONLY
+                            );
+                            if output_fd == -1 {
+                                println!("Error when opening file {}", output);
+                                return -4;
+                            }
+                            let output_fd = output_fd as usize;
+                            close(1);
+                            assert_eq!(dup(output_fd), 1);
+                            close(output_fd);
+                        }
                         // child process
-                        if exec(line.as_str()) == -1 {
+                        if exec(args_copy[0].as_str(), args_addr.as_slice()) == -1 {
                             println!("Error when executing!");
                             return -4;
                         }
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 9be723f..9204c08 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -1,21 +1,23 @@
 #![no_std]
 #![feature(asm)]
 #![feature(linkage)]
-#![feature(alloc_error_handler)]
 #![feature(panic_info_message)]
-
-#[macro_use]
-extern crate bitflags;
+#![feature(alloc_error_handler)]
 
 #[macro_use]
 pub mod console;
-mod lang;
 mod scall_os;
+mod lang;
+
+extern crate alloc;
+#[macro_use]
+extern crate bitflags;
 
-use buddy_system_allocator::LockedHeap;
 use scall_os::*;
+use buddy_system_allocator::LockedHeap;
+use alloc::vec::Vec;
 
-const USER_HEAP_SIZE: usize = 16384;
+const USER_HEAP_SIZE: usize = 32768;
 
 static mut HEAP_SPACE: [u8; USER_HEAP_SIZE] = [0; USER_HEAP_SIZE];
 
@@ -29,17 +31,31 @@ pub fn handle_alloc_error(layout: core::alloc::Layout) -> ! {
 
 #[no_mangle]
 #[link_section = ".text.entry"]
-pub extern "C" fn _start() -> ! {
-     unsafe {
+pub extern "C" fn _start(argc: usize, argv: usize) -> ! {
+    unsafe {
         HEAP.lock()
             .init(HEAP_SPACE.as_ptr() as usize, USER_HEAP_SIZE);
     }
-    exit(main());
+    let mut v: Vec<&'static str> = Vec::new();
+    for i in 0..argc {
+        let str_start = unsafe {
+            ((argv + i * core::mem::size_of::<usize>()) as *const usize).read_volatile()
+        };
+        let len = (0usize..).find(|i| unsafe {
+            ((str_start + *i) as *const u8).read_volatile() == 0
+        }).unwrap();
+        v.push(
+            core::str::from_utf8(unsafe {
+                core::slice::from_raw_parts(str_start as *const u8, len)
+            }).unwrap()
+        );
+    }
+    exit(main(argc, v.as_slice()));
 }
 
 #[linkage = "weak"]
 #[no_mangle]
-fn main() -> i32 {
+fn main(_argc: usize, _argv: &[&str]) -> i32 {
     panic!("Cannot find main!");
 }
 
@@ -64,7 +80,7 @@ pub fn yield_() -> isize { sys_yield() }
 pub fn get_time() -> isize { sys_get_time() }
 pub fn getpid() -> isize { sys_getpid() }
 pub fn fork() -> isize { sys_fork() }
-pub fn exec(path: &str) -> isize { sys_exec(path) }
+pub fn exec(path: &str, args: &[*const u8]) -> isize { sys_exec(path, args) }
 pub fn wait(exit_code: &mut i32) -> isize {
     loop {
         match sys_waitpid(-1, exit_code as *mut _) {
diff --git a/user/src/scall_os.rs b/user/src/scall_os.rs
index 6047858..9315753 100644
--- a/user/src/scall_os.rs
+++ b/user/src/scall_os.rs
@@ -72,8 +72,8 @@ pub fn sys_fork() -> isize {
     syscall(SYSCALL_FORK, [0, 0, 0])
 }
 
-pub fn sys_exec(path: &str) -> isize {
-    syscall(SYSCALL_EXEC, [path.as_ptr() as usize, 0, 0])
+pub fn sys_exec(path: &str, args: &[*const u8]) -> isize {
+    syscall(SYSCALL_EXEC, [path.as_ptr() as usize, args.as_ptr() as usize, 0])
 }
 
 pub fn sys_waitpid(pid: isize, exit_code: *mut i32) -> isize {