Use IS_CONSOLE macro to detect that we're indeed using a console

programs/util.c

@@ -90,6 +90,10 @@ int g_utilDisplayLevel;
 int UTIL_requireUserConfirmation(const char* prompt, const char* abortMsg,
                                           const char* acceptableLetters) {
     int ch, result;
+    /* If input is presented via stdin, dont use prompt as it may swallow characters */
+    if (!IS_CONSOLE(stdin))
+        return 0;
+
     UTIL_DISPLAY("%s", prompt);
     ch = getchar();
     result = 0;

tests/playTests.sh

@@ -309,7 +309,6 @@ test -f precompressedFilterTestDir/input.5.zst.zst
 test -f precompressedFilterTestDir/input.6.zst.zst
 println "Test completed"
 
-
 println "\n===>  recursive mode test "
 # combination of -r with empty list of input file
 zstd -c -r < tmp > tmp.zst