Playground: add support for I/O redirection (< > >>)

Parse < (stdin from file), > (stdout to file), and >> (append) in
the command line. Files are read from and written to the persistent
virtual filesystem, so redirected output persists across commands.

static/js/wasm-terminal.js

@@ -331,49 +331,101 @@ async function runCommand(argv, stdinData = "") {
 
 /**
  * Parse a command line into a pipeline of commands.
- * Supports simple pipes: cmd1 | cmd2 | cmd3
- * Pipes inside quotes are treated as literal characters.
+ * Supports pipes (|), input redirection (<), and output redirection (>, >>).
+ * Returns an array of stages: { args: string[], stdin: string|null, stdout: string|null, append: boolean }
  */
 function parseCommandLine(line) {
-  const pipeline = [[]];
+  // First, tokenize respecting quotes
+  const tokens = [];
   let current = "";
   let inSingle = false;
   let inDouble = false;
   let escape = false;
 
   for (const ch of line) {
-    if (escape) {
-      current += ch;
-      escape = false;
-      continue;
-    }
-    if (ch === "\\" && !inSingle) {
-      escape = true;
-      continue;
-    }
-    if (ch === "'" && !inDouble) {
-      inSingle = !inSingle;
-      continue;
-    }
-    if (ch === '"' && !inSingle) {
-      inDouble = !inDouble;
-      continue;
-    }
-    if (ch === "|" && !inSingle && !inDouble) {
-      if (current) { pipeline[pipeline.length - 1].push(current); current = ""; }
-      pipeline.push([]);
-      continue;
-    }
-    if (ch === " " && !inSingle && !inDouble) {
-      if (current) { pipeline[pipeline.length - 1].push(current); current = ""; }
+    if (escape) { current += ch; escape = false; continue; }
+    if (ch === "\\" && !inSingle) { escape = true; continue; }
+    if (ch === "'" && !inDouble) { inSingle = !inSingle; continue; }
+    if (ch === '"' && !inSingle) { inDouble = !inDouble; continue; }
+    if (!inSingle && !inDouble && (ch === "|" || ch === "<" || ch === ">" || ch === " ")) {
+      if (current) { tokens.push(current); current = ""; }
+      if (ch !== " ") tokens.push(ch);
       continue;
     }
     current += ch;
   }
-  if (current) pipeline[pipeline.length - 1].push(current);
+  if (current) tokens.push(current);
+
+  // Merge >> into a single token
+  for (let i = 0; i < tokens.length - 1; i++) {
+    if (tokens[i] === ">" && tokens[i + 1] === ">") {
+      tokens.splice(i, 2, ">>");
+    }
+  }
+
+  // Split into pipeline stages and extract redirections
+  const pipeline = [];
+  let stage = { args: [], stdin: null, stdout: null, append: false };
+
+  for (let i = 0; i < tokens.length; i++) {
+    const tok = tokens[i];
+    if (tok === "|") {
+      pipeline.push(stage);
+      stage = { args: [], stdin: null, stdout: null, append: false };
+    } else if (tok === "<" && i + 1 < tokens.length) {
+      stage.stdin = tokens[++i];
+    } else if ((tok === ">" || tok === ">>") && i + 1 < tokens.length) {
+      stage.append = tok === ">>";
+      stage.stdout = tokens[++i];
+    } else {
+      stage.args.push(tok);
+    }
+  }
+  pipeline.push(stage);
   return pipeline;
 }
 
+/**
+ * Read a file from the virtual filesystem. Returns its content as a string,
+ * or null if not found.
+ */
+function readVirtualFile(name) {
+  const dir = getPersistentDir();
+  const resolved = resolvePath(name);
+  const parts = resolved.split("/").filter(Boolean);
+  let current = dir.dir;
+  for (let i = 0; i < parts.length - 1; i++) {
+    const entry = current.contents.get(parts[i]);
+    if (!entry || !entry.contents) return null;
+    current = entry;
+  }
+  const file = current.contents.get(parts[parts.length - 1] || name);
+  if (!file || !file.data) return null;
+  return new TextDecoder().decode(file.data);
+}
+
+/**
+ * Write a file to the virtual filesystem.
+ */
+function writeVirtualFile(name, content, append) {
+  const dir = getPersistentDir();
+  const resolved = resolvePath(name);
+  const encoder = new TextEncoder();
+  const existing = dir.dir.contents.get(resolved);
+  let data;
+  if (append && existing && existing.data) {
+    const prev = existing.data;
+    const added = encoder.encode(content);
+    data = new Uint8Array(prev.length + added.length);
+    data.set(prev);
+    data.set(added, prev.length);
+  } else {
+    data = encoder.encode(content);
+  }
+  const file = new wasiShim.File(data);
+  dir.dir.contents.set(resolved, file);
+}
+
 /**
  * Execute a full command line, handling pipes and builtins.
  */
@@ -446,9 +498,17 @@ async function executeCommandLine(line) {
   const pipeline = parseCommandLine(line);
   let stdinData = "";
 
-  for (const args of pipeline) {
+  for (const stage of pipeline) {
+    const { args, stdin: stdinFile, stdout: stdoutFile, append } = stage;
     if (args.length === 0) continue;
 
+    // Handle input redirection: < file
+    if (stdinFile) {
+      const content = readVirtualFile(stdinFile);
+      if (content === null) return `${stdinFile}: No such file\n`;
+      stdinData = content;
+    }
+
     const cmd = args[0];
 
     // Try WASM execution for commands in the WASM build
@@ -472,20 +532,24 @@ async function executeCommandLine(line) {
           return result.stderr + result.stdout;
         }
         stdinData = result.stdout;
-        continue;
       } catch (e) {
         return `Error running '${cmd}': ${e.message}\n`;
       }
+    } else {
+      // JS fallback for commands not in the WASM build or when WASM isn't ready
+      const result = jsFallback(args, stdinData);
+      if (result !== null) {
+        stdinData = result;
+      } else {
+        return `uutils: command not found: ${cmd}\nType 'help' for available commands.\n`;
+      }
     }
 
-    // JS fallback for commands not in the WASM build or when WASM isn't ready
-    const result = jsFallback(args, stdinData);
-    if (result !== null) {
-      stdinData = result;
-      continue;
+    // Handle output redirection: > file or >> file
+    if (stdoutFile) {
+      writeVirtualFile(stdoutFile, stdinData, append);
+      stdinData = "";
     }
-
-    return `uutils: command not found: ${cmd}\nType 'help' for available commands.\n`;
   }
 
   return stdinData;
@@ -880,6 +944,8 @@ window._uutilsTestInternals = {
   resolvePath,
   lookupDir,
   getPersistentDir,
+  readVirtualFile,
+  writeVirtualFile,
   get cwd() { return cwd; },
   set cwd(v) { cwd = v; },
   get locale() { return currentLocale; },

static/js/wasm-terminal.test.html

@@ -20,7 +20,7 @@
 <script>
 (async function() {
 const T = window._uutilsTestInternals;
-const { parseCommandLine, jsFallback, executeCommandLine, resolvePath, lookupDir, getPersistentDir, SAMPLE_FILES, AVAILABLE_COMMANDS } = T;
+const { parseCommandLine, jsFallback, executeCommandLine, resolvePath, lookupDir, getPersistentDir, readVirtualFile, writeVirtualFile, SAMPLE_FILES, AVAILABLE_COMMANDS } = T;
 
 let passed = 0;
 let failed = 0;
@@ -71,54 +71,77 @@ async function runTests() {
   // ===== parseCommandLine =====
   section("parseCommandLine");
 
+  // Helper: extract just args arrays from parsed pipeline for simpler assertions
+  const argsOf = (p) => p.map(s => s.args);
+
   assertDeep("simple command",
-    parseCommandLine("echo hello"),
+    argsOf(parseCommandLine("echo hello")),
     [["echo", "hello"]]);
 
   assertDeep("multiple args",
-    parseCommandLine("wc -l fruits.txt"),
+    argsOf(parseCommandLine("wc -l fruits.txt")),
     [["wc", "-l", "fruits.txt"]]);
 
   assertDeep("pipe",
-    parseCommandLine("echo hello | wc -c"),
+    argsOf(parseCommandLine("echo hello | wc -c")),
     [["echo", "hello"], ["wc", "-c"]]);
 
   assertDeep("double pipe",
-    parseCommandLine("cat file | sort | uniq"),
+    argsOf(parseCommandLine("cat file | sort | uniq")),
     [["cat", "file"], ["sort"], ["uniq"]]);
 
   assertDeep("single quotes",
-    parseCommandLine("echo 'hello world'"),
+    argsOf(parseCommandLine("echo 'hello world'")),
     [["echo", "hello world"]]);
 
   assertDeep("double quotes",
-    parseCommandLine('echo "hello world"'),
+    argsOf(parseCommandLine('echo "hello world"')),
     [["echo", "hello world"]]);
 
   assertDeep("escaped space",
-    parseCommandLine("echo hello\\ world"),
+    argsOf(parseCommandLine("echo hello\\ world")),
     [["echo", "hello world"]]);
 
   assertDeep("mixed quotes",
-    parseCommandLine("echo 'it\"s' \"a test\""),
+    argsOf(parseCommandLine("echo 'it\"s' \"a test\"")),
     [["echo", 'it"s', "a test"]]);
 
   assertDeep("empty input",
-    parseCommandLine(""),
+    argsOf(parseCommandLine("")),
     [[]]);
 
   assertDeep("multiple spaces",
-    parseCommandLine("echo   hello    world"),
+    argsOf(parseCommandLine("echo   hello    world")),
     [["echo", "hello", "world"]]);
 
   assertDeep("pipe inside single quotes is literal",
-    parseCommandLine("echo 'a|b'"),
+    argsOf(parseCommandLine("echo 'a|b'")),
     [["echo", "a|b"]]);
 
   assertDeep("pipe inside double quotes is literal",
-    parseCommandLine('echo "a|b"'),
+    argsOf(parseCommandLine('echo "a|b"')),
     [["echo", "a|b"]]);
 
+  // Redirection parsing
+  let p = parseCommandLine("sort < input.txt");
+  assertDeep("stdin redirect args", p[0].args, ["sort"]);
+  assert("stdin redirect file", p[0].stdin, "input.txt");
+
+  p = parseCommandLine("echo hello > output.txt");
+  assertDeep("stdout redirect args", p[0].args, ["echo", "hello"]);
+  assert("stdout redirect file", p[0].stdout, "output.txt");
+  assert("stdout redirect not append", p[0].append, false);
+
+  p = parseCommandLine("echo hello >> output.txt");
+  assert("append redirect file", p[0].stdout, "output.txt");
+  assert("append redirect flag", p[0].append, true);
+
+  p = parseCommandLine("sort < in.txt | head -3 > out.txt");
+  assert("pipe + redirect: stdin", p[0].stdin, "in.txt");
+  assertDeep("pipe + redirect: first args", p[0].args, ["sort"]);
+  assert("pipe + redirect: stdout", p[1].stdout, "out.txt");
+  assertDeep("pipe + redirect: second args", p[1].args, ["head", "-3"]);
+
   // ===== jsFallback: echo =====
   section("jsFallback: echo");
 
@@ -578,6 +601,39 @@ async function runTests() {
   assert("complete 'sh' includes shuf", r.candidates.includes("shuf"), true);
   assert("complete 'sh' includes shred", r.candidates.includes("shred"), true);
 
+  // ===== I/O redirection =====
+  section("I/O redirection");
+
+  // > creates a file
+  await executeCommandLine("echo 'hello redirect' > redir_test.txt");
+  assert("> creates file",
+    readVirtualFile("redir_test.txt"), "hello redirect\n");
+
+  // < reads from file
+  await assertAsync("< reads file as stdin",
+    executeCommandLine("wc -c < redir_test.txt"),
+    "15\n");
+
+  // >> appends
+  await executeCommandLine("echo 'line2' >> redir_test.txt");
+  assert(">> appends to file",
+    readVirtualFile("redir_test.txt"), "hello redirect\nline2\n");
+
+  // > overwrites
+  await executeCommandLine("echo 'overwritten' > redir_test.txt");
+  assert("> overwrites file",
+    readVirtualFile("redir_test.txt"), "overwritten\n");
+
+  // pipe + redirect
+  await executeCommandLine("echo '3\n1\n2' | sort > sorted.txt");
+  assert("pipe | sort > file",
+    readVirtualFile("sorted.txt"), "1\n2\n3\n");
+
+  // < with nonexistent file
+  await assertAsync("< nonexistent file",
+    executeCommandLine("sort < no_such_file.txt"),
+    "no_such_file.txt: No such file\n");
+
   // ===== Summary =====
   const summary = document.getElementById("summary");
   const total = passed + failed;