feat(userspace): shell runs programs (ls, cat) via spawn w/ terminal+storage+args page; ext4 holes read as zeros; storage re-attach same buffer

crates/apps/cat/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "cat"
+version = "0.1.0"
+edition = "2024"
+
+[[bin]]
+name = "cat"
+test = false
+bench = false
+
+[dependencies]
+types = { workspace = true }
+libkos = { workspace = true }

crates/apps/cat/src/main.rs

@@ -0,0 +1,45 @@
+//! Prints files: `cat <file>...`.
+
+#![no_std]
+#![no_main]
+
+extern crate libkos;
+
+use libkos::fs::{FsError, Storage};
+use libkos::println;
+
+/// Where storage's buffer is mapped.
+const STORAGE_BUF_VA: usize = 0x0180_0000;
+
+fn cat(fs: &mut Storage, path: &str) -> Result<(), FsError> {
+    let h = fs.open(path.as_bytes())?;
+    let mut buf = [0u8; 4096];
+    loop {
+        let n = fs.read(h, &mut buf)?;
+        libkos::io::write_bytes(&buf[..n]);
+        if n < buf.len() {
+            break;
+        }
+    }
+    fs.close(h)
+}
+
+#[unsafe(no_mangle)]
+extern "C" fn main() {
+    let Some(mut fs) = libkos::start::storage().and_then(|ep| Storage::attach(ep, STORAGE_BUF_VA).ok()) else {
+        println!("cat: no storage");
+        return;
+    };
+    let mut any = false;
+    for path in libkos::start::args().skip(1) {
+        any = true;
+        match cat(&mut fs, path) {
+            Ok(()) => {}
+            Err(FsError::NotFound) => println!("cat: {}: no such file", path),
+            Err(_) => println!("cat: {}: cannot read", path),
+        }
+    }
+    if !any {
+        println!("usage: cat <file>...");
+    }
+}