feat(builtins): add 21 missing everyday commands, fix N>file redirects

crates/bashkit-js/__test__/runtime-compat/security.test.mjs

@@ -48,7 +48,7 @@ describe("security", () => {
 
   it("sandbox escape blocked", () => {
     const bash = new Bash();
-    assert.notEqual(bash.executeSync("exec /bin/bash").exitCode, 0);
+    assert.notEqual(bash.executeSync("exec /usr/bin/gcc").exitCode, 0);
     assert.notEqual(bash.executeSync("cat /proc/self/maps 2>&1").exitCode, 0);
     assert.ok(!bash.executeSync("cat /etc/passwd 2>&1").stdout.includes("root:x:0:0"));
     assert.notEqual(

crates/bashkit-js/__test__/security.spec.ts

@@ -221,8 +221,11 @@ test("WB: stderr truncation on massive error output", (t) => {
 test("WB: exec cannot escape sandbox (TM-ESC-001)", (t) => {
   const bash = new Bash();
   // exec runs commands within VFS sandbox — external binaries don't exist
-  const r = bash.executeSync("exec /bin/bash");
+  const r = bash.executeSync("exec /usr/bin/gcc");
   t.not(r.exitCode, 0, "exec of external binary must fail in sandbox");
+  // /bin/bash is a rootfs stub that re-enters the in-process interpreter
+  const inner = bash.executeSync("exec /bin/bash -c 'cat /etc/passwd'");
+  t.false(inner.stdout.includes("root:x:0:0"), "host passwd must not leak");
 });
 
 test("WB: /proc filesystem not accessible (TM-ESC-003)", (t) => {

crates/bashkit/docs/compatibility.md

@@ -191,6 +191,21 @@ Chrono's validated strftime implementation, plus GNU `%N`, `%3N`, `%6N`, and
 | `mktemp` | `-d`, `-p`, `-t` | Create temporary files |
 | `realpath` | `PATH` | Resolve path |
 | `pushd`/`popd`/`dirs` | standard flags | Directory stack |
+| `arch` | (none) | Virtual machine name (`x86_64`) |
+| `sum` | `-r`, `-s` | BSD and System V checksums, GNU output format |
+| `shasum` | `-a 1/224/256/384/512` | Perl `shasum` front end over the `sha*sum` builtins |
+| `egrep`/`fgrep` | `grep` flags | `grep -E` / `grep -F` |
+| `link`/`unlink` | `FILE1 FILE2` / `FILE` | Single-file link (a symlink, L-FS-001) and remove |
+| `chgrp` | `GROUP FILE...` | Change group (virtual, like `chown`) |
+| `nohup`/`nice` | `COMMAND...`, `nice -n N` | Run the command; no signal or priority effect in a sandbox |
+| `flock` | `FILE CMD`, `FILE -c CMD`, `-n FD` | Creates the lock file and runs the command; locks are uncontended in one session |
+| `getconf` | `NAME`, `-a` | POSIX config values, consistent with `nproc` and `/proc/meminfo` |
+| `tty` | `-s` | "not a tty" unless the embedder sets `tty(0, true)`, like `[ -t 0 ]` |
+| `sync`/`hostid` | (none) | No-op / fixed virtual host id |
+| `groups`/`logname` | `[USER]` | Virtual user only |
+| `users`/`who` | (none) | Empty: no login sessions |
+| `uptime` | `-p`, `-s` | Derived from the virtual clock |
+| `free` | `-b`, `-k`, `-m`, `-g`, `-h`, `-t` | Fixed virtual memory, consistent with `/proc/meminfo` |
 
 ### Not Implemented
 
@@ -225,6 +240,7 @@ Chrono's validated strftime implementation, plus GNU `%N`, `%3N`, `%6N`, and
 | `2>` | ✅ | `cmd 2> file` | Stderr redirect |
 | `2>&1` | ✅ | `cmd 2>&1` | Stderr to stdout |
 | `&>` | ✅ | `cmd &> file` | Both to file |
+| `N>`/`N>>` (N≥3) | ✅ | `{ cmd >&3; } 3>file` | Opens fd N only; stdout untouched |
 
 ### Control Flow
 

crates/bashkit/docs/threat-model.md

@@ -207,7 +207,7 @@ Scripts may attempt to break out of the sandbox to access the host system.
 
 | Threat | Attack Example | Mitigation | Status |
 |--------|---------------|------------|--------|
-| Shell escape (TM-ESC-005) | `exec /bin/bash` | Not implemented (exit 127) | MITIGATED |
+| Shell escape (TM-ESC-005) | `exec /bin/bash` | Re-enters the in-process interpreter; host binaries are unreachable (exit 127) | MITIGATED |
 | External commands (TM-ESC-006) | `./malicious` | Runs in VFS sandbox, no host shell | MITIGATED |
 | Background proc (TM-ESC-007) | `malicious &` | Background not implemented | MITIGATED |
 | eval injection (TM-ESC-008) | `eval "$input"` | Sandboxed eval (builtins only) | MITIGATED |

crates/bashkit/src/builtins/checksum.rs

@@ -79,11 +79,20 @@ async fn read_operand(ctx: &Context<'_>, file: &str) -> std::result::Result<Vec<
 }
 
 async fn checksum_execute<D: Digest>(ctx: &Context<'_>, cmd: &str) -> Result<ExecResult> {
+    checksum_execute_args::<D>(ctx, cmd, ctx.args).await
+}
+
+/// [`checksum_execute`] over explicit arguments (`shasum` strips `-a N`).
+pub(super) async fn checksum_execute_args<D: Digest>(
+    ctx: &Context<'_>,
+    cmd: &str,
+    args: &[String],
+) -> Result<ExecResult> {
     let mut files: Vec<&str> = Vec::new();
     let mut end_of_options = false;
     let mut opts = CheckOpts::default();
 
-    for arg in ctx.args {
+    for arg in args {
         if end_of_options || arg == "-" || !arg.starts_with('-') {
             files.push(arg);
             continue;