feat: implement streq and printErr

user/redirreader.c

@@ -0,0 +1,57 @@
+#include "ulib.h"
+
+/*
+ * Companion to redirwriter.c -- reads fd 0 (redirected by the shell to a
+ * REAL file via `<`, jobctlApplyRedirects) in a loop until a real EOF (a
+ * regular file's own vfsRead already returns 0 the instant the offset
+ * reaches its size -- no writer-count bookkeeping needed the way
+ * pipesink.c's pipe-backed EOF does, since a file's "end" is just its
+ * length, not "every writer has gone away"), then compares byte-for-byte
+ * against two back-to-back copies of redirwriter.c's own payload -- proof
+ * that `>` (create/truncate) followed by `>>` (append) on the SAME path
+ * produced exactly that file, not a truncated/duplicated/reordered one.
+ *
+ * Unlike pipesink.c, this process's own fd 1 (stdout) is NOT redirected --
+ * print()/printDec() (ulib.h) reach the real console exactly like any
+ * unredirected demo, so the needle below is exactly as observable to
+ * ci-test.sh as every other one.
+ */
+
+static int streq(const char* a, const char* b)
+{
+    while (*a && *a == *b) {
+        a++;
+        b++;
+    }
+    return *a == *b;
+}
+
+int main(void)
+{
+    print("redirreader: reading redirected stdin\n");
+
+    char buffer[80];
+    unsigned long total = 0;
+    for (;;) {
+        long got = userRead(0, buffer + total, sizeof(buffer) - 1 - total);
+        if (got < 0) {
+            print("redirreader: FAIL read\n");
+            return 1;
+        }
+        if (got == 0)
+            break;
+        total += (unsigned long)got;
+        if (total >= sizeof(buffer) - 1)
+            break;
+    }
+    buffer[total] = 0;
+
+    print("redirreader: got: ");
+    print(buffer);
+    print("\n");
+
+    int ok = streq(buffer, "redirect-payload-okredirect-payload-ok");
+    print(ok ? "redirreader: payload-ok\n" : "redirreader: payload-FAIL\n");
+
+    return ok ? 0 : 1;
+}