Updates

kernel/bin/truncate

@@ -87,30 +87,54 @@ function bareOsEmitRaw(ctx, chunk) {
   return false
 }
 
+/**
+ * @param {string} raw
+ * @param {number} curLen
+ * @returns {number | null}
+ */
+function resolveTruncateSize(raw, curLen) {
+  const s = String(raw).trim()
+  if (!s) return null
+  if (/%$/.test(s)) {
+    const inner = s.startsWith('+') || s.startsWith('-') ? s.slice(1) : s
+    const pct = Number.parseFloat(inner.replace(/%$/, ''))
+    if (!Number.isFinite(pct)) return null
+    const delta = Math.floor((curLen * pct) / 100)
+    if (s.startsWith('+')) return Math.max(0, curLen + delta)
+    if (s.startsWith('-')) return Math.max(0, curLen - delta)
+    return Math.max(0, Math.floor((curLen * pct) / 100))
+  }
+  if (s.startsWith('+')) {
+    const n = Number.parseInt(s.slice(1), 10)
+    if (!Number.isFinite(n)) return null
+    return Math.max(0, curLen + n)
+  }
+  if (s.startsWith('-')) {
+    const n = Number.parseInt(s.slice(1), 10)
+    if (!Number.isFinite(n)) return null
+    return Math.max(0, curLen - n)
+  }
+  const abs = Number.parseInt(s, 10)
+  if (!Number.isFinite(abs) || abs < 0) return null
+  return abs
+}
+
 async function run(ctx, argv) {
-  let size = null
+  /** @type {string | null} */
+  let sizeSpec = null
   const paths = []
   for (let i = 1; i < argv.length; i++) {
     const a = argv[i]
     if (a === '-h' || a === '--help') {
       ctx.console.log(
-        'usage: truncate -s SIZE FILE\nSet file length to SIZE bytes (padded with zeros if growing).'
+        'usage: truncate -s SIZE FILE\n' +
+          'SIZE: bytes, +N, -N, +N%, -N%, or N% (of current length).\n' +
+          'Sets file length (padded with zeros if growing).'
       )
       return
     }
     if ((a === '-s' || a === '--size') && argv[i + 1]) {
-      const raw = argv[++i]
-      if (raw.startsWith('+') || raw.startsWith('-')) {
-        ctx.console.error('truncate: relative sizes not supported')
-        ctx.exitCode = 1
-        return
-      }
-      size = parseInt(raw, 10)
-      if (!Number.isFinite(size) || size < 0) {
-        ctx.console.error('truncate: invalid size')
-        ctx.exitCode = 1
-        return
-      }
+      sizeSpec = argv[++i]
       continue
     }
     if (a.startsWith('-')) {
@@ -120,7 +144,7 @@ async function run(ctx, argv) {
     }
     paths.push(a)
   }
-  if (size == null || paths.length !== 1) {
+  if (!sizeSpec || paths.length !== 1) {
     ctx.console.error('usage: truncate -s SIZE FILE')
     ctx.exitCode = 1
     return
@@ -131,7 +155,13 @@ async function run(ctx, argv) {
     const b = await ctx.vfs.readFile(file)
     if (b) cur = b instanceof Uint8Array ? b : new Uint8Array(b)
   } catch {
-    /* new file */
+    /* new file — relative sizes use curLen 0 */
+  }
+  const size = resolveTruncateSize(sizeSpec, cur.length)
+  if (size == null) {
+    ctx.console.error('truncate: invalid size: ' + sizeSpec)
+    ctx.exitCode = 1
+    return
   }
   const out = new Uint8Array(size)
   out.set(cur.subarray(0, Math.min(cur.length, size)))