diff --git a/.arclint b/.arclint
--- a/.arclint
+++ b/.arclint
@@ -63,7 +63,7 @@
             "type": "lint-locale-dependence",
             "include": "(^src/.*\\.(h|cpp)$)",
             "exclude": [
-                "(^src/(crypto/ctaes/|leveldb/|secp256k1/|seeder/|tinyformat.h|univalue/))"
+                "(^src/(crypto/ctaes/|leveldb/|secp256k1/|tinyformat.h|univalue/))"
             ]
         },
         "lint-cheader": {
diff --git a/arcanist/linter/LocaleDependenceLinter.php b/arcanist/linter/LocaleDependenceLinter.php
--- a/arcanist/linter/LocaleDependenceLinter.php
+++ b/arcanist/linter/LocaleDependenceLinter.php
@@ -32,6 +32,12 @@
       "split",
       "is_space",
     ],
+    "src/seeder/main.cpp" => [
+        "strtoull",
+        "strcasecmp",
+        "strftime",
+    ],
+    "src/seeder/dns.cpp" => ["strcasecmp"],
     "src/torcontrol.cpp" => [
       "atoi",
       "strtol",
@@ -64,7 +70,7 @@
     "fgetwc",
     "fgetws",
     "fold_case",   // boost::locale::fold_case
-    //"fprintf"      // (via vfprintf)
+    "fprintf",     // (via vfprintf)
     "fputwc",
     "fputws",
     "fscanf",      // (via __vfscanf)
@@ -111,7 +117,7 @@
     "mbtowc",      // LC_CTYPE
     "mktime",
     "normalize",   // boost::locale::normalize
-    //"printf"       // LC_NUMERIC
+    "printf",      // LC_NUMERIC
     "putwc",
     "putwchar",
     "scanf",       // LC_NUMERIC
diff --git a/src/bench/bench_bitcoin.cpp b/src/bench/bench_bitcoin.cpp
--- a/src/bench/bench_bitcoin.cpp
+++ b/src/bench/bench_bitcoin.cpp
@@ -70,8 +70,8 @@
     SetupBenchArgs();
     std::string error;
     if (!gArgs.ParseParameters(argc, argv, error)) {
-        fprintf(stderr, "Error parsing command line arguments: %s\n",
-                error.c_str());
+        tfm::format(std::cerr, "Error parsing command line arguments: %s\n",
+                    error.c_str());
         return EXIT_FAILURE;
     }
 
@@ -87,8 +87,8 @@
 
     double scaling_factor;
     if (!ParseDouble(scaling_str, &scaling_factor)) {
-        fprintf(stderr, "Error parsing scaling factor as double: %s\n",
-                scaling_str.c_str());
+        tfm::format(std::cerr, "Error parsing scaling factor as double: %s\n",
+                    scaling_str.c_str());
         return EXIT_FAILURE;
     }
 
diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -153,8 +153,8 @@
     SetupCliArgs();
     std::string error;
     if (!gArgs.ParseParameters(argc, argv, error)) {
-        fprintf(stderr, "Error parsing command line arguments: %s\n",
-                error.c_str());
+        tfm::format(std::cerr, "Error parsing command line arguments: %s\n",
+                    error.c_str());
         return EXIT_FAILURE;
     }
     if (argc < 2 || HelpRequested(gArgs) || gArgs.IsArgSet("-version")) {
@@ -175,22 +175,22 @@
             strUsage += "\n" + gArgs.GetHelpMessage();
         }
 
-        fprintf(stdout, "%s", strUsage.c_str());
+        tfm::format(std::cout, "%s", strUsage.c_str());
         if (argc < 2) {
-            fprintf(stderr, "Error: too few parameters\n");
+            tfm::format(std::cerr, "Error: too few parameters\n");
             return EXIT_FAILURE;
         }
         return EXIT_SUCCESS;
     }
     if (!fs::is_directory(GetDataDir(false))) {
-        fprintf(stderr,
-                "Error: Specified data directory \"%s\" does not exist.\n",
-                gArgs.GetArg("-datadir", "").c_str());
+        tfm::format(std::cerr,
+                    "Error: Specified data directory \"%s\" does not exist.\n",
+                    gArgs.GetArg("-datadir", "").c_str());
         return EXIT_FAILURE;
     }
     if (!gArgs.ReadConfigFiles(error, true)) {
-        fprintf(stderr, "Error reading configuration file: %s\n",
-                error.c_str());
+        tfm::format(std::cerr, "Error reading configuration file: %s\n",
+                    error.c_str());
         return EXIT_FAILURE;
     }
     // Check for -testnet or -regtest parameter (BaseParams() calls are only
@@ -198,7 +198,7 @@
     try {
         SelectBaseParams(gArgs.GetChainName());
     } catch (const std::exception &e) {
-        fprintf(stderr, "Error: %s\n", e.what());
+        tfm::format(std::cerr, "Error: %s\n", e.what());
         return EXIT_FAILURE;
     }
     return CONTINUE_EXECUTION;
@@ -615,7 +615,8 @@
     }
 
     if (strPrint != "") {
-        fprintf((nRet == 0 ? stdout : stderr), "%s\n", strPrint.c_str());
+        tfm::format(nRet == 0 ? std::cout : std::cerr, "%s\n",
+                    strPrint.c_str());
     }
     return nRet;
 }
@@ -627,7 +628,7 @@
 #endif
     SetupEnvironment();
     if (!SetupNetworking()) {
-        fprintf(stderr, "Error: Initializing networking failed\n");
+        tfm::format(std::cerr, "Error: Initializing networking failed\n");
         return EXIT_FAILURE;
     }
     event_set_log_callback(&libevent_log_cb);
diff --git a/src/bitcoin-tx.cpp b/src/bitcoin-tx.cpp
--- a/src/bitcoin-tx.cpp
+++ b/src/bitcoin-tx.cpp
@@ -109,8 +109,8 @@
     SetupBitcoinTxArgs();
     std::string error;
     if (!gArgs.ParseParameters(argc, argv, error)) {
-        fprintf(stderr, "Error parsing command line arguments: %s\n",
-                error.c_str());
+        tfm::format(std::cerr, "Error parsing command line arguments: %s\n",
+                    error.c_str());
         return EXIT_FAILURE;
     }
 
@@ -119,7 +119,7 @@
     try {
         SelectParams(gArgs.GetChainName());
     } catch (const std::exception &e) {
-        fprintf(stderr, "Error: %s\n", e.what());
+        tfm::format(std::cerr, "Error: %s\n", e.what());
         return EXIT_FAILURE;
     }
 
@@ -136,10 +136,10 @@
             "hex-encoded bitcoin transaction\n" +
             "\n";
         strUsage += gArgs.GetHelpMessage();
-        fprintf(stdout, "%s", strUsage.c_str());
+        tfm::format(std::cout, "%s", strUsage.c_str());
 
         if (argc < 2) {
-            fprintf(stderr, "Error: too few parameters\n");
+            tfm::format(std::cerr, "Error: too few parameters\n");
             return EXIT_FAILURE;
         }
 
@@ -763,20 +763,20 @@
     TxToUniv(tx, uint256(), entry);
 
     std::string jsonOutput = entry.write(4);
-    fprintf(stdout, "%s\n", jsonOutput.c_str());
+    tfm::format(std::cout, "%s\n", jsonOutput.c_str());
 }
 
 static void OutputTxHash(const CTransaction &tx) {
     // the hex-encoded transaction id.
     std::string strHexHash = tx.GetId().GetHex();
 
-    fprintf(stdout, "%s\n", strHexHash.c_str());
+    tfm::format(std::cout, "%s\n", strHexHash.c_str());
 }
 
 static void OutputTxHex(const CTransaction &tx) {
     std::string strHex = EncodeHexTx(tx);
 
-    fprintf(stdout, "%s\n", strHex.c_str());
+    tfm::format(std::cout, "%s\n", strHex.c_str());
 }
 
 static void OutputTx(const CTransaction &tx) {
@@ -871,7 +871,8 @@
     }
 
     if (strPrint != "") {
-        fprintf((nRet == 0 ? stdout : stderr), "%s\n", strPrint.c_str());
+        tfm::format(nRet == 0 ? std::cout : std::cerr, "%s\n",
+                    strPrint.c_str());
     }
 
     return nRet;
diff --git a/src/bitcoin-wallet.cpp b/src/bitcoin-wallet.cpp
--- a/src/bitcoin-wallet.cpp
+++ b/src/bitcoin-wallet.cpp
@@ -50,8 +50,8 @@
     SetupWalletToolArgs();
     std::string error_message;
     if (!gArgs.ParseParameters(argc, argv, error_message)) {
-        fprintf(stderr, "Error parsing command line arguments: %s\n",
-                error_message.c_str());
+        tfm::format(std::cerr, "Error parsing command line arguments: %s\n",
+                    error_message.c_str());
         return false;
     }
     if (argc < 2 || HelpRequested(gArgs)) {
@@ -67,7 +67,7 @@
             "Usage:\n" + "  bitcoin-wallet [options] <command>\n\n" +
             gArgs.GetHelpMessage();
 
-        fprintf(stdout, "%s", usage.c_str());
+        tfm::format(std::cout, "%s", usage.c_str());
         return false;
     }
 
@@ -76,9 +76,9 @@
         gArgs.GetBoolArg("-printtoconsole", gArgs.GetBoolArg("-debug", false));
 
     if (!fs::is_directory(GetDataDir(false))) {
-        fprintf(stderr,
-                "Error: Specified data directory \"%s\" does not exist.\n",
-                gArgs.GetArg("-datadir", "").c_str());
+        tfm::format(std::cerr,
+                    "Error: Specified data directory \"%s\" does not exist.\n",
+                    gArgs.GetArg("-datadir", "").c_str());
         return false;
     }
     // Check for -testnet or -regtest parameter (Params() calls are only valid
@@ -111,10 +111,10 @@
     for (int i = 1; i < argc; ++i) {
         if (!IsSwitchChar(argv[i][0])) {
             if (!method.empty()) {
-                fprintf(stderr,
-                        "Error: two methods provided (%s and %s). Only one "
-                        "method should be provided.\n",
-                        method.c_str(), argv[i]);
+                tfm::format(std::cerr,
+                            "Error: two methods provided (%s and %s). Only one "
+                            "method should be provided.\n",
+                            method.c_str(), argv[i]);
                 return EXIT_FAILURE;
             }
             method = argv[i];
@@ -122,15 +122,17 @@
     }
 
     if (method.empty()) {
-        fprintf(stderr, "No method provided. Run `bitcoin-wallet -help` for "
-                        "valid methods.\n");
+        tfm::format(std::cerr,
+                    "No method provided. Run `bitcoin-wallet -help` for "
+                    "valid methods.\n");
         return EXIT_FAILURE;
     }
 
     // A name must be provided when creating a file
     if (method == "create" && !gArgs.IsArgSet("-wallet")) {
-        fprintf(stderr,
-                "Wallet name must be provided when creating a new wallet.\n");
+        tfm::format(
+            std::cerr,
+            "Wallet name must be provided when creating a new wallet.\n");
         return EXIT_FAILURE;
     }
 
diff --git a/src/bitcoind.cpp b/src/bitcoind.cpp
--- a/src/bitcoind.cpp
+++ b/src/bitcoind.cpp
@@ -83,8 +83,8 @@
     SetupServerArgs();
     std::string error;
     if (!gArgs.ParseParameters(argc, argv, error)) {
-        fprintf(stderr, "Error parsing command line arguments: %s\n",
-                error.c_str());
+        tfm::format(std::cerr, "Error parsing command line arguments: %s\n",
+                    error.c_str());
         return false;
     }
 
@@ -102,20 +102,21 @@
             strUsage += "\n" + gArgs.GetHelpMessage();
         }
 
-        fprintf(stdout, "%s", strUsage.c_str());
+        tfm::format(std::cout, "%s", strUsage.c_str());
         return true;
     }
 
     try {
         if (!fs::is_directory(GetDataDir(false))) {
-            fprintf(stderr,
-                    "Error: Specified data directory \"%s\" does not exist.\n",
-                    gArgs.GetArg("-datadir", "").c_str());
+            tfm::format(
+                std::cerr,
+                "Error: Specified data directory \"%s\" does not exist.\n",
+                gArgs.GetArg("-datadir", "").c_str());
             return false;
         }
         if (!gArgs.ReadConfigFiles(error, true)) {
-            fprintf(stderr, "Error reading configuration file: %s\n",
-                    error.c_str());
+            tfm::format(std::cerr, "Error reading configuration file: %s\n",
+                        error.c_str());
             return false;
         }
         // Check for -testnet or -regtest parameter (Params() calls are only
@@ -123,7 +124,7 @@
         try {
             SelectParams(gArgs.GetChainName());
         } catch (const std::exception &e) {
-            fprintf(stderr, "Error: %s\n", e.what());
+            tfm::format(std::cerr, "Error: %s\n", e.what());
             return false;
         }
 
@@ -141,10 +142,11 @@
         // line
         for (int i = 1; i < argc; i++) {
             if (!IsSwitchChar(argv[i][0])) {
-                fprintf(stderr,
-                        "Error: Command line contains unexpected token '%s', "
-                        "see bitcoind -h for a list of options.\n",
-                        argv[i]);
+                tfm::format(
+                    std::cerr,
+                    "Error: Command line contains unexpected token '%s', "
+                    "see bitcoind -h for a list of options.\n",
+                    argv[i]);
                 return false;
             }
         }
@@ -176,21 +178,21 @@
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 #endif
-            fprintf(stdout, "Bitcoin server starting\n");
+            tfm::format(std::cout, "Bitcoin server starting\n");
 
             // Daemonize
             if (daemon(1, 0)) {
                 // don't chdir (1), do close FDs (0)
-                fprintf(stderr, "Error: daemon() failed: %s\n",
-                        strerror(errno));
+                tfm::format(std::cerr, "Error: daemon() failed: %s\n",
+                            strerror(errno));
                 return false;
             }
 #if defined(MAC_OSX)
 #pragma GCC diagnostic pop
 #endif
 #else
-            fprintf(
-                stderr,
+            tfm::format(
+                std::cerr,
                 "Error: -daemon is not supported on this operating system\n");
             return false;
 #endif // HAVE_DECL_DAEMON
diff --git a/src/init.cpp b/src/init.cpp
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -104,14 +104,13 @@
 }
 
 NODISCARD static bool CreatePidFile() {
-    FILE *file = fsbridge::fopen(GetPidFile(), "w");
+    fsbridge::ofstream file{GetPidFile()};
     if (file) {
 #ifdef WIN32
-        fprintf(file, "%d\n", GetCurrentProcessId());
+        tfm::format(file, "%d\n", GetCurrentProcessId());
 #else
-        fprintf(file, "%d\n", getpid());
+        tfm::format(file, "%d\n", getpid());
 #endif
-        fclose(file);
         return true;
     } else {
         return InitError(strprintf(_("Unable to create the PID file '%s': %s"),
diff --git a/src/noui.cpp b/src/noui.cpp
--- a/src/noui.cpp
+++ b/src/noui.cpp
@@ -45,7 +45,7 @@
     if (!fSecure) {
         LogPrintf("%s: %s\n", strCaption, message);
     }
-    fprintf(stderr, "%s: %s\n", strCaption.c_str(), message.c_str());
+    tfm::format(std::cerr, "%s: %s\n", strCaption.c_str(), message.c_str());
     return false;
 }
 
diff --git a/src/qt/utilitydialog.cpp b/src/qt/utilitydialog.cpp
--- a/src/qt/utilitydialog.cpp
+++ b/src/qt/utilitydialog.cpp
@@ -127,7 +127,7 @@
 void HelpMessageDialog::printToConsole() {
     // On other operating systems, the expected action is to print the message
     // to the console.
-    fprintf(stdout, "%s\n", qPrintable(text));
+    tfm::format(std::cout, "%s\n", qPrintable(text));
 }
 
 void HelpMessageDialog::showOrPrint() {
diff --git a/src/seeder/bitcoin.cpp b/src/seeder/bitcoin.cpp
--- a/src/seeder/bitcoin.cpp
+++ b/src/seeder/bitcoin.cpp
@@ -26,7 +26,8 @@
     nHeaderStart = vSend.size();
     vSend << CMessageHeader(netMagic, pszCommand, 0);
     nMessageStart = vSend.size();
-    // fprintf(stdout, "%s: SEND %s\n", ToString(you).c_str(), pszCommand);
+    // tfm::format(std::cout, "%s: SEND %s\n", ToString(you).c_str(),
+    // pszCommand);
 }
 
 void CSeederNode::AbortMessage() {
@@ -92,7 +93,7 @@
 
 PeerMessagingState CSeederNode::ProcessMessage(std::string strCommand,
                                                CDataStream &recv) {
-    // fprintf(stdout, "%s: RECV %s\n", ToString(you).c_str(),
+    // tfm::format(std::cout, "%s: RECV %s\n", ToString(you).c_str(),
     // strCommand.c_str());
     if (strCommand == "version") {
         int64_t nTime;
@@ -114,7 +115,7 @@
 
     if (strCommand == "verack") {
         vRecv.SetVersion(std::min(nVersion, PROTOCOL_VERSION));
-        // fprintf(stdout, "\n%s: version %i\n", ToString(you).c_str(),
+        // tfm::format(std::cout, "\n%s: version %i\n", ToString(you).c_str(),
         // nVersion);
         if (vAddr) {
             BeginMessage("getaddr");
@@ -129,7 +130,8 @@
     if (strCommand == "addr" && vAddr) {
         std::vector<CAddress> vAddrNew;
         recv >> vAddrNew;
-        // fprintf(stdout, "%s: got %i addresses\n", ToString(you).c_str(),
+        // tfm::format(std::cout, "%s: got %i addresses\n",
+        // ToString(you).c_str(),
         //        (int)vAddrNew.size());
         int64_t now = time(nullptr);
         std::vector<CAddress>::iterator it = vAddrNew.begin();
@@ -140,7 +142,7 @@
         }
         while (it != vAddrNew.end()) {
             CAddress &addr = *it;
-            // fprintf(stdout, "%s: got address %s\n",
+            // tfm::format(std::cout, "%s: got address %s\n",
             // ToString(you).c_str(),
             //        addr.ToString().c_str(), (int)(vAddr->size()));
             it++;
@@ -150,7 +152,7 @@
             if (addr.nTime > now - 604800) {
                 vAddr->push_back(addr);
             }
-            // fprintf(stdout, "%s: added address %s (#%i)\n",
+            // tfm::format(std::cout, "%s: added address %s (#%i)\n",
             // ToString(you).c_str(),
             //        addr.ToString().c_str(), (int)(vAddr->size()));
             if (vAddr->size() > ADDR_SOFT_CAP) {
@@ -186,7 +188,7 @@
         CMessageHeader hdr(netMagic);
         vRecv >> hdr;
         if (!hdr.IsValidWithoutConfig(netMagic)) {
-            // fprintf(stdout, "%s: BAD (invalid header)\n",
+            // tfm::format(std::cout, "%s: BAD (invalid header)\n",
             // ToString(you).c_str());
             ban = 100000;
             return true;
@@ -194,7 +196,7 @@
         std::string strCommand = hdr.GetCommand();
         unsigned int nMessageSize = hdr.nMessageSize;
         if (nMessageSize > MAX_SIZE) {
-            // fprintf(stdout, "%s: BAD (message too large)\n",
+            // tfm::format(std::cout, "%s: BAD (message too large)\n",
             // ToString(you).c_str());
             ban = 100000;
             return true;
@@ -216,7 +218,7 @@
         if (ProcessMessage(strCommand, vMsg) == PeerMessagingState::Finished) {
             return true;
         }
-        // fprintf(stdout, "%s: done processing %s\n",
+        // tfm::format(std::cout, "%s: done processing %s\n",
         // ToString(you).c_str(),
         //        strCommand.c_str());
     } while (1);
@@ -262,7 +264,8 @@
     }
 
     if (!connected) {
-        // fprintf(stdout, "Cannot connect to %s\n", ToString(you).c_str());
+        // tfm::format(std::cout, "Cannot connect to %s\n",
+        // ToString(you).c_str());
         CloseSocket(sock);
         return false;
     }
@@ -303,12 +306,13 @@
             vRecv.resize(nPos + nBytes);
             memcpy(&vRecv[nPos], pchBuf, nBytes);
         } else if (nBytes == 0) {
-            // fprintf(stdout, "%s: BAD (connection closed prematurely)\n",
+            // tfm::format(std::cout, "%s: BAD (connection closed
+            // prematurely)\n",
             //        ToString(you).c_str());
             res = false;
             break;
         } else {
-            // fprintf(stdout, "%s: BAD (connection error)\n",
+            // tfm::format(std::cout, "%s: BAD (connection error)\n",
             // ToString(you).c_str());
             res = false;
             break;
@@ -338,8 +342,8 @@
         clientV = node.GetClientVersion();
         clientSV = node.GetClientSubVersion();
         blocks = node.GetStartingHeight();
-        // fprintf(stdout, "%s: %s!!!\n", cip.ToString().c_str(), ret ? "GOOD" :
-        // "BAD");
+        // tfm::format(std::cout, "%s: %s!!!\n", cip.ToString().c_str(), ret ?
+        // "GOOD" : "BAD");
         return ret;
     } catch (std::ios_base::failure &e) {
         ban = 0;
diff --git a/src/seeder/db.cpp b/src/seeder/db.cpp
--- a/src/seeder/db.cpp
+++ b/src/seeder/db.cpp
@@ -28,7 +28,7 @@
     if (ign && (ignoreTill == 0 || ignoreTill < ign + now)) {
         ignoreTill = ign + now;
     }
-    //  fprintf(stdout, "%s: got %s result: success=%i/%i;
+    //  tfm::format(std::cout, "%s: got %s result: success=%i/%i;
     //  2H:%.2f%%-%.2f%%(%.2f) 8H:%.2f%%-%.2f%%(%.2f) 1D:%.2f%%-%.2f%%(%.2f)
     //  1W:%.2f%%-%.2f%%(%.2f) \n", ToString(ip).c_str(), good ? "good" : "bad",
     //  success, total, 100.0 * stat2H.reliability, 100.0 * (stat2H.reliability
@@ -99,7 +99,7 @@
     info.Update(true);
     if (info.IsGood() && goodId.count(id) == 0) {
         goodId.insert(id);
-        //    fprintf(stdout, "%s: good; %i good nodes now\n",
+        //    tfm::format(std::cout, "%s: good; %i good nodes now\n",
         //    ToString(addr).c_str(), (int)goodId.size());
     }
     nDirty++;
@@ -117,13 +117,13 @@
     uint32_t now = time(nullptr);
     int ter = info.GetBanTime();
     if (ter) {
-        //    fprintf(stdout, "%s: terrible\n", ToString(addr).c_str());
+        //    tfm::format(std::cout, "%s: terrible\n", ToString(addr).c_str());
         if (ban < ter) {
             ban = ter;
         }
     }
     if (ban > 0) {
-        //    fprintf(stdout, "%s: ban for %i seconds\n",
+        //    tfm::format(std::cout, "%s: ban for %i seconds\n",
         //    ToString(addr).c_str(), ban);
         banned[info.ip] = ban + now;
         ipToId.erase(info.ip);
@@ -132,7 +132,7 @@
     } else {
         if (/*!info.IsGood() && */ goodId.count(id) == 1) {
             goodId.erase(id);
-            //      fprintf(stdout, "%s: not good; %i good nodes left\n",
+            //      tfm::format(std::cout, "%s: not good; %i good nodes left\n",
             //      ToString(addr).c_str(), (int)goodId.size());
         }
         ourId.push_back(id);
@@ -158,7 +158,8 @@
         if (addr.nTime > ai.lastTry || ai.services != addr.nServices) {
             ai.lastTry = addr.nTime;
             ai.services |= addr.nServices;
-            //      fprintf(stdout, "%s: updated\n", ToString(addr).c_str());
+            //      tfm::format(std::cout, "%s: updated\n",
+            //      ToString(addr).c_str());
         }
         if (force) {
             ai.ignoreTill = 0;
@@ -176,7 +177,8 @@
     int id = nId++;
     idToInfo[id] = ai;
     ipToId[ipp] = id;
-    //  fprintf(stdout, "%s: added\n", ToString(ipp).c_str(), ipToId[ipp]);
+    //  tfm::format(std::cout, "%s: added\n", ToString(ipp).c_str(),
+    //  ipToId[ipp]);
     unkId.insert(id);
     nDirty++;
 }
diff --git a/src/seeder/dns.cpp b/src/seeder/dns.cpp
--- a/src/seeder/dns.cpp
+++ b/src/seeder/dns.cpp
@@ -385,14 +385,14 @@
     outbuf[3] &= ~15;
     // check qr
     if (inbuf[2] & 128) {
-        /* fprintf(stdout, "Got response?\n"); */
+        /* tfm::format(std::cout, "Got response?\n"); */
         responseCode = DNSResponseCode::FORMAT_ERROR;
         goto error;
     }
 
     // check opcode
     if (((inbuf[2] & 120) >> 3) != 0) {
-        /* fprintf(stdout, "Opcode nonzero?\n"); */
+        /* tfm::format(std::cout, "Opcode nonzero?\n"); */
         responseCode = DNSResponseCode::NOT_IMPLEMENTED;
         goto error;
     }
@@ -404,13 +404,13 @@
     // check questions
     nquestion = (inbuf[4] << 8) + inbuf[5];
     if (nquestion == 0) {
-        /* fprintf(stdout, "No questions?\n"); */
+        /* tfm::format(std::cout, "No questions?\n"); */
         responseCode = DNSResponseCode::OK;
         goto error;
     }
 
     if (nquestion > 1) {
-        /* fprintf(stdout, "Multiple questions %i?\n", nquestion); */
+        /* tfm::format(std::cout, "Multiple questions %i?\n", nquestion); */
         responseCode = DNSResponseCode::NOT_IMPLEMENTED;
         goto error;
     }
@@ -466,8 +466,8 @@
         uint8_t *outpos = outbuf + (inpos - inbuf);
         uint8_t *outend = outbuf + BUFLEN;
 
-        //   fprintf(stdout, "DNS: Request host='%s' type=%i class=%i\n", name,
-        //   typ, cls);
+        //   tfm::format(std::cout, "DNS: Request host='%s' type=%i class=%i\n",
+        //   name, typ, cls);
 
         // calculate max size of authority section
 
@@ -485,8 +485,8 @@
             if (max_auth_size < newpos - outpos) {
                 max_auth_size = newpos - outpos;
             }
-            //    fprintf(stdout, "Authority section will claim %i bytes max\n",
-            //    max_auth_size);
+            //    tfm::format(std::cout, "Authority section will claim %i bytes
+            //    max\n", max_auth_size);
         }
 
         // Answer section
@@ -496,7 +496,7 @@
             (cls == CLASS_IN || cls == QCLASS_ANY)) {
             int ret2 = write_record_ns(&outpos, outend - max_auth_size, "",
                                        offset, CLASS_IN, opt->nsttl, opt->ns);
-            //    fprintf(stdout, "wrote NS record: %i\n", ret2);
+            //    tfm::format(std::cout, "wrote NS record: %i\n", ret2);
             if (!ret2) {
                 outbuf[7]++;
                 have_ns++;
@@ -510,7 +510,7 @@
                 write_record_soa(&outpos, outend - max_auth_size, "", offset,
                                  CLASS_IN, opt->nsttl, opt->ns, opt->mbox,
                                  time(NULL), 604800, 86400, 2592000, 604800);
-            //    fprintf(stdout, "wrote SOA record: %i\n", ret2);
+            //    tfm::format(std::cout, "wrote SOA record: %i\n", ret2);
             if (!ret2) {
                 outbuf[7]++;
             }
@@ -536,7 +536,8 @@
                         opt->datattl, &addr[n]);
                 }
 
-                //      fprintf(stdout, "wrote A record: %i\n", mustbreak);
+                //      tfm::format(std::cout, "wrote A record: %i\n",
+                //      mustbreak);
                 if (mustbreak) {
                     break;
                 }
@@ -550,7 +551,7 @@
         if (!have_ns && outbuf[7]) {
             int ret2 = write_record_ns(&outpos, outend, "", offset, CLASS_IN,
                                        opt->nsttl, opt->ns);
-            //    fprintf(stdout, "wrote NS record: %i\n", ret2);
+            //    tfm::format(std::cout, "wrote NS record: %i\n", ret2);
             if (!ret2) {
                 outbuf[9]++;
             }
@@ -562,7 +563,7 @@
             int ret2 = write_record_soa(
                 &outpos, outend, "", offset, CLASS_IN, opt->nsttl, opt->ns,
                 opt->mbox, time(NULL), 604800, 86400, 2592000, 604800);
-            //    fprintf(stdout, "wrote SOA record: %i\n", ret2);
+            //    tfm::format(std::cout, "wrote SOA record: %i\n", ret2);
             if (!ret2) {
                 outbuf[9]++;
             }
@@ -644,9 +645,9 @@
     for (; 1; ++(opt->nRequests)) {
         ssize_t insize = recvmsg(listenSocket, &msg, 0);
         //    uint8_t *addr = (uint8_t*)&si_other.sin_addr.s_addr;
-        //    fprintf(stdout, "DNS: Request %llu from %i.%i.%i.%i:%i of %i
-        //    bytes\n", (unsigned long long)(opt->nRequests), addr[0], addr[1],
-        //    addr[2], addr[3], ntohs(si_other.sin_port), (int)insize);
+        //    tfm::format(std::cout, "DNS: Request %llu from %i.%i.%i.%i:%i of
+        //    %i bytes\n", (unsigned long long)(opt->nRequests), addr[0],
+        //    addr[1], addr[2], addr[3], ntohs(si_other.sin_port), (int)insize);
         if (insize <= 0) {
             continue;
         }
diff --git a/src/seeder/main.cpp b/src/seeder/main.cpp
--- a/src/seeder/main.cpp
+++ b/src/seeder/main.cpp
@@ -63,8 +63,8 @@
         SetupSeederArgs();
         std::string error;
         if (!gArgs.ParseParameters(argc, argv, error)) {
-            fprintf(stderr, "Error parsing command line arguments: %s\n",
-                    error.c_str());
+            tfm::format(std::cerr, "Error parsing command line arguments: %s\n",
+                        error.c_str());
             return EXIT_FAILURE;
         }
         if (HelpRequested(gArgs) || gArgs.IsArgSet("-version")) {
@@ -77,7 +77,7 @@
                     gArgs.GetHelpMessage();
             }
 
-            fprintf(stdout, "%s", strUsage.c_str());
+            tfm::format(std::cout, "%s", strUsage.c_str());
             return EXIT_SUCCESS;
         }
 
@@ -377,13 +377,14 @@
                 }
                 rename("dnsseed.dat.new", "dnsseed.dat");
             }
-            FILE *d = fsbridge::fopen("dnsseed.dump", "w");
-            fprintf(d, "# address                                        good  "
-                       "lastSuccess    %%(2h)   %%(8h)   %%(1d)   %%(7d)  "
-                       "%%(30d)  blocks      svcs  version\n");
+            fsbridge::ofstream d{"dnsseed.dump"};
+            tfm::format(
+                d, "# address                                        good  "
+                   "lastSuccess    %%(2h)   %%(8h)   %%(1d)   %%(7d)  "
+                   "%%(30d)  blocks      svcs  version\n");
             double stat[5] = {0, 0, 0, 0, 0};
             for (CAddrReport rep : v) {
-                fprintf(
+                tfm::format(
                     d,
                     "%-47s  %4d  %11" PRId64
                     "  %6.2f%% %6.2f%% %6.2f%% %6.2f%% %6.2f%%  %6i  %08" PRIx64
@@ -399,12 +400,10 @@
                 stat[3] += rep.uptime[3];
                 stat[4] += rep.uptime[4];
             }
-            fclose(d);
-            FILE *ff = fsbridge::fopen("dnsstats.log", "a");
-            fprintf(ff, "%llu %g %g %g %g %g\n",
-                    (unsigned long long)(time(nullptr)), stat[0], stat[1],
-                    stat[2], stat[3], stat[4]);
-            fclose(ff);
+            fsbridge::ofstream ff{"dnsstats.log", std::ios_base::app};
+            tfm::format(ff, "%llu %g %g %g %g %g\n",
+                        (unsigned long long)(time(nullptr)), stat[0], stat[1],
+                        stat[2], stat[3], stat[4]);
         }
     } while (1);
     return nullptr;
@@ -421,24 +420,25 @@
         db.GetStats(stats);
         if (first) {
             first = false;
-            fprintf(stdout, "\n\n\n\x1b[3A");
+            tfm::format(std::cout, "\n\n\n\x1b[3A");
         } else {
-            fprintf(stdout, "\x1b[2K\x1b[u");
+            tfm::format(std::cout, "\x1b[2K\x1b[u");
         }
-        fprintf(stdout, "\x1b[s");
+        tfm::format(std::cout, "\x1b[s");
         uint64_t requests = 0;
         uint64_t queries = 0;
         for (unsigned int i = 0; i < dnsThread.size(); i++) {
             requests += dnsThread[i]->dns_opt.nRequests;
             queries += dnsThread[i]->dbQueries;
         }
-        fprintf(stdout,
-                "%s %i/%i available (%i tried in %is, %i new, %i active), %i "
-                "banned; %llu DNS requests, %llu db queries\n",
-                c, stats.nGood, stats.nAvail, stats.nTracked, stats.nAge,
-                stats.nNew, stats.nAvail - stats.nTracked - stats.nNew,
-                stats.nBanned, (unsigned long long)requests,
-                (unsigned long long)queries);
+        tfm::format(
+            std::cout,
+            "%s %i/%i available (%i tried in %is, %i new, %i active), %i "
+            "banned; %llu DNS requests, %llu db queries\n",
+            c, stats.nGood, stats.nAvail, stats.nTracked, stats.nAge,
+            stats.nNew, stats.nAvail - stats.nTracked - stats.nNew,
+            stats.nBanned, (unsigned long long)requests,
+            (unsigned long long)queries);
         Sleep(1000);
     } while (1);
     return nullptr;
@@ -473,87 +473,87 @@
         return parseResults;
     }
 
-    fprintf(stdout, "Supporting whitelisted filters: ");
+    tfm::format(std::cout, "Supporting whitelisted filters: ");
     for (std::set<uint64_t>::const_iterator it = opts.filter_whitelist.begin();
          it != opts.filter_whitelist.end(); it++) {
         if (it != opts.filter_whitelist.begin()) {
-            fprintf(stdout, ",");
+            tfm::format(std::cout, ",");
         }
-        fprintf(stdout, "0x%lx", (unsigned long)*it);
+        tfm::format(std::cout, "0x%lx", (unsigned long)*it);
     }
-    fprintf(stdout, "\n");
+    tfm::format(std::cout, "\n");
     if (!opts.tor.empty()) {
         CService service(LookupNumeric(opts.tor.c_str(), 9050));
         if (service.IsValid()) {
-            fprintf(stdout, "Using Tor proxy at %s\n",
-                    service.ToStringIPPort().c_str());
+            tfm::format(std::cout, "Using Tor proxy at %s\n",
+                        service.ToStringIPPort().c_str());
             SetProxy(NET_ONION, proxyType(service));
         }
     }
     if (!opts.ipv4_proxy.empty()) {
         CService service(LookupNumeric(opts.ipv4_proxy.c_str(), 9050));
         if (service.IsValid()) {
-            fprintf(stdout, "Using IPv4 proxy at %s\n",
-                    service.ToStringIPPort().c_str());
+            tfm::format(std::cout, "Using IPv4 proxy at %s\n",
+                        service.ToStringIPPort().c_str());
             SetProxy(NET_IPV4, proxyType(service));
         }
     }
     if (!opts.ipv6_proxy.empty()) {
         CService service(LookupNumeric(opts.ipv6_proxy.c_str(), 9050));
         if (service.IsValid()) {
-            fprintf(stdout, "Using IPv6 proxy at %s\n",
-                    service.ToStringIPPort().c_str());
+            tfm::format(std::cout, "Using IPv6 proxy at %s\n",
+                        service.ToStringIPPort().c_str());
             SetProxy(NET_IPV6, proxyType(service));
         }
     }
     bool fDNS = true;
-    fprintf(stdout, "Using %s.\n", gArgs.GetChainName().c_str());
+    tfm::format(std::cout, "Using %s.\n", gArgs.GetChainName().c_str());
     netMagic = Params().NetMagic();
     if (opts.ns.empty()) {
-        fprintf(stdout, "No nameserver set. Not starting DNS server.\n");
+        tfm::format(std::cout, "No nameserver set. Not starting DNS server.\n");
         fDNS = false;
     }
     if (fDNS && opts.host.empty()) {
-        fprintf(stderr, "No hostname set. Please use -h.\n");
+        tfm::format(std::cerr, "No hostname set. Please use -h.\n");
         return EXIT_FAILURE;
     }
     if (fDNS && opts.mbox.empty()) {
-        fprintf(stderr, "No e-mail address set. Please use -m.\n");
+        tfm::format(std::cerr, "No e-mail address set. Please use -m.\n");
         return EXIT_FAILURE;
     }
     FILE *f = fsbridge::fopen("dnsseed.dat", "r");
     if (f) {
-        fprintf(stdout, "Loading dnsseed.dat...");
+        tfm::format(std::cout, "Loading dnsseed.dat...");
         CAutoFile cf(f, SER_DISK, CLIENT_VERSION);
         cf >> db;
         if (opts.fWipeBan) {
             db.banned.clear();
-            fprintf(stdout, "Ban list wiped...");
+            tfm::format(std::cout, "Ban list wiped...");
         }
         if (opts.fWipeIgnore) {
             db.ResetIgnores();
-            fprintf(stdout, "Ignore list wiped...");
+            tfm::format(std::cout, "Ignore list wiped...");
         }
-        fprintf(stdout, "done\n");
+        tfm::format(std::cout, "done\n");
     }
     pthread_t threadDns, threadSeed, threadDump, threadStats;
     if (fDNS) {
-        fprintf(stdout, "Starting %i DNS threads for %s on %s (port %i)...",
-                opts.nDnsThreads, opts.host.c_str(), opts.ns.c_str(),
-                opts.nPort);
+        tfm::format(
+            std::cout, "Starting %i DNS threads for %s on %s (port %i)...",
+            opts.nDnsThreads, opts.host.c_str(), opts.ns.c_str(), opts.nPort);
         dnsThread.clear();
         for (int i = 0; i < opts.nDnsThreads; i++) {
             dnsThread.push_back(new CDnsThread(&opts, i));
             pthread_create(&threadDns, nullptr, ThreadDNS, dnsThread[i]);
-            fprintf(stdout, ".");
+            tfm::format(std::cout, ".");
             Sleep(20);
         }
-        fprintf(stdout, "done\n");
+        tfm::format(std::cout, "done\n");
     }
-    fprintf(stdout, "Starting seeder...");
+    tfm::format(std::cout, "Starting seeder...");
     pthread_create(&threadSeed, nullptr, ThreadSeeder, nullptr);
-    fprintf(stdout, "done\n");
-    fprintf(stdout, "Starting %i crawler threads...", opts.nThreads);
+    tfm::format(std::cout, "done\n");
+    tfm::format(std::cout, "Starting %i crawler threads...", opts.nThreads);
     pthread_attr_t attr_crawler;
     pthread_attr_init(&attr_crawler);
     pthread_attr_setstacksize(&attr_crawler, 0x20000);
@@ -562,7 +562,7 @@
         pthread_create(&thread, &attr_crawler, ThreadCrawler, &opts.nThreads);
     }
     pthread_attr_destroy(&attr_crawler);
-    fprintf(stdout, "done\n");
+    tfm::format(std::cout, "done\n");
     pthread_create(&threadStats, nullptr, ThreadStats, nullptr);
     pthread_create(&threadDump, nullptr, ThreadDumper, nullptr);
     void *res;
diff --git a/src/sync.cpp b/src/sync.cpp
--- a/src/sync.cpp
+++ b/src/sync.cpp
@@ -41,9 +41,9 @@
           m_thread_name(thread_name), sourceLine(nLine) {}
 
     std::string ToString() const {
-        return tfm::format("%s %s:%s%s (in thread %s)", mutexName, sourceFile,
-                           itostr(sourceLine), (fTry ? " (TRY)" : ""),
-                           m_thread_name);
+        return strprintf("%s %s:%s%s (in thread %s)", mutexName, sourceFile,
+                         itostr(sourceLine), (fTry ? " (TRY)" : ""),
+                         m_thread_name);
     }
 
 private:
@@ -103,10 +103,11 @@
         LogPrintf(" %s\n", i.second.ToString());
     }
     if (g_debug_lockorder_abort) {
-        fprintf(stderr,
-                "Assertion failed: detected inconsistent lock order at %s:%i, "
-                "details in debug log.\n",
-                __FILE__, __LINE__);
+        tfm::format(
+            std::cerr,
+            "Assertion failed: detected inconsistent lock order at %s:%i, "
+            "details in debug log.\n",
+            __FILE__, __LINE__);
         abort();
     }
     throw std::logic_error("potential deadlock detected");
@@ -167,9 +168,9 @@
             return;
         }
     }
-    fprintf(stderr,
-            "Assertion failed: lock %s not held in %s:%i; locks held:\n%s",
-            pszName, pszFile, nLine, LocksHeld().c_str());
+    tfm::format(std::cerr,
+                "Assertion failed: lock %s not held in %s:%i; locks held:\n%s",
+                pszName, pszFile, nLine, LocksHeld().c_str());
     abort();
 }
 
@@ -177,9 +178,10 @@
                                int nLine, void *cs) {
     for (const std::pair<void *, CLockLocation> &i : g_lockstack) {
         if (i.first == cs) {
-            fprintf(stderr,
-                    "Assertion failed: lock %s held in %s:%i; locks held:\n%s",
-                    pszName, pszFile, nLine, LocksHeld().c_str());
+            tfm::format(
+                std::cerr,
+                "Assertion failed: lock %s held in %s:%i; locks held:\n%s",
+                pszName, pszFile, nLine, LocksHeld().c_str());
             abort();
         }
     }
diff --git a/src/tinyformat.h b/src/tinyformat.h
--- a/src/tinyformat.h
+++ b/src/tinyformat.h
@@ -1085,6 +1085,10 @@
 
 } // namespace tinyformat
 
+/**
+ * Format arguments and return the string or write to given std::ostream (see
+ * tinyformat::format doc for details)
+ */
 #define strprintf tfm::format
 
 #endif // TINYFORMAT_H_INCLUDED
diff --git a/src/util/system.cpp b/src/util/system.cpp
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -779,7 +779,8 @@
 void PrintExceptionContinue(const std::exception *pex, const char *pszThread) {
     std::string message = FormatException(pex, pszThread);
     LogPrintf("\n\n************************\n%s\n", message);
-    fprintf(stderr, "\n\n************************\n%s\n", message.c_str());
+    tfm::format(std::cerr, "\n\n************************\n%s\n",
+                message.c_str());
 }
 
 fs::path GetDefaultDataDir() {
@@ -1072,10 +1073,11 @@
                 }
             }
             for (const std::string &to_include : includeconf) {
-                fprintf(stderr,
-                        "warning: -includeconf cannot be used from included "
-                        "files; ignoring -includeconf=%s\n",
-                        to_include.c_str());
+                tfm::format(
+                    std::cerr,
+                    "warning: -includeconf cannot be used from included "
+                    "files; ignoring -includeconf=%s\n",
+                    to_include.c_str());
             }
         }
     }
diff --git a/src/wallet/wallettool.cpp b/src/wallet/wallettool.cpp
--- a/src/wallet/wallettool.cpp
+++ b/src/wallet/wallettool.cpp
@@ -26,7 +26,7 @@
 static std::shared_ptr<CWallet> CreateWallet(const std::string &name,
                                              const fs::path &path) {
     if (fs::exists(path)) {
-        fprintf(stderr, "Error: File exists already\n");
+        tfm::format(std::cerr, "Error: File exists already\n");
         return nullptr;
     }
     // dummy chain interface
@@ -38,7 +38,7 @@
     bool first_run = true;
     DBErrors load_wallet_ret = wallet_instance->LoadWallet(first_run);
     if (load_wallet_ret != DBErrors::LOAD_OK) {
-        fprintf(stderr, "Error creating %s", name.c_str());
+        tfm::format(std::cerr, "Error creating %s", name.c_str());
         return nullptr;
     }
 
@@ -48,7 +48,7 @@
     CPubKey seed = wallet_instance->GenerateNewSeed();
     wallet_instance->SetHDSeed(seed);
 
-    fprintf(stdout, "Topping up keypool...\n");
+    tfm::format(std::cout, "Topping up keypool...\n");
     wallet_instance->TopUpKeyPool();
     return wallet_instance;
 }
@@ -56,7 +56,7 @@
 static std::shared_ptr<CWallet> LoadWallet(const std::string &name,
                                            const fs::path &path) {
     if (!fs::exists(path)) {
-        fprintf(stderr, "Error: Wallet files does not exist\n");
+        tfm::format(std::cerr, "Error: Wallet files does not exist\n");
         return nullptr;
     }
 
@@ -71,35 +71,38 @@
         bool first_run;
         load_wallet_ret = wallet_instance->LoadWallet(first_run);
     } catch (const std::runtime_error &) {
-        fprintf(stderr,
-                "Error loading %s. Is wallet being used by another process?\n",
-                name.c_str());
+        tfm::format(
+            std::cerr,
+            "Error loading %s. Is wallet being used by another process?\n",
+            name.c_str());
         return nullptr;
     }
 
     if (load_wallet_ret != DBErrors::LOAD_OK) {
         wallet_instance = nullptr;
         if (load_wallet_ret == DBErrors::CORRUPT) {
-            fprintf(stderr, "Error loading %s: Wallet corrupted", name.c_str());
+            tfm::format(std::cerr, "Error loading %s: Wallet corrupted",
+                        name.c_str());
             return nullptr;
         } else if (load_wallet_ret == DBErrors::NONCRITICAL_ERROR) {
-            fprintf(stderr,
-                    "Error reading %s! All keys read correctly, but "
-                    "transaction data"
-                    " or address book entries might be missing or incorrect.",
-                    name.c_str());
+            tfm::format(
+                std::cerr,
+                "Error reading %s! All keys read correctly, but "
+                "transaction data"
+                " or address book entries might be missing or incorrect.",
+                name.c_str());
         } else if (load_wallet_ret == DBErrors::TOO_NEW) {
-            fprintf(stderr,
-                    "Error loading %s: Wallet requires newer version of %s",
-                    name.c_str(), PACKAGE_NAME);
+            tfm::format(std::cerr,
+                        "Error loading %s: Wallet requires newer version of %s",
+                        name.c_str(), PACKAGE_NAME);
             return nullptr;
         } else if (load_wallet_ret == DBErrors::NEED_REWRITE) {
-            fprintf(stderr,
-                    "Wallet needed to be rewritten: restart %s to complete",
-                    PACKAGE_NAME);
+            tfm::format(std::cerr,
+                        "Wallet needed to be rewritten: restart %s to complete",
+                        PACKAGE_NAME);
             return nullptr;
         } else {
-            fprintf(stderr, "Error loading %s", name.c_str());
+            tfm::format(std::cerr, "Error loading %s", name.c_str());
             return nullptr;
         }
     }
@@ -111,15 +114,17 @@
     // lock required because of some AssertLockHeld()
     LOCK(wallet_instance->cs_wallet);
 
-    fprintf(stdout, "Wallet info\n===========\n");
-    fprintf(stdout, "Encrypted: %s\n",
-            wallet_instance->IsCrypted() ? "yes" : "no");
-    fprintf(stdout, "HD (hd seed available): %s\n",
-            wallet_instance->GetHDChain().seed_id.IsNull() ? "no" : "yes");
-    fprintf(stdout, "Keypool Size: %u\n", wallet_instance->GetKeyPoolSize());
-    fprintf(stdout, "Transactions: %zu\n", wallet_instance->mapWallet.size());
-    fprintf(stdout, "Address Book: %zu\n",
-            wallet_instance->mapAddressBook.size());
+    tfm::format(std::cout, "Wallet info\n===========\n");
+    tfm::format(std::cout, "Encrypted: %s\n",
+                wallet_instance->IsCrypted() ? "yes" : "no");
+    tfm::format(std::cout, "HD (hd seed available): %s\n",
+                wallet_instance->GetHDChain().seed_id.IsNull() ? "no" : "yes");
+    tfm::format(std::cout, "Keypool Size: %u\n",
+                wallet_instance->GetKeyPoolSize());
+    tfm::format(std::cout, "Transactions: %zu\n",
+                wallet_instance->mapWallet.size());
+    tfm::format(std::cout, "Address Book: %zu\n",
+                wallet_instance->mapAddressBook.size());
 }
 
 bool ExecuteWalletToolFunc(const std::string &command,
@@ -134,13 +139,14 @@
         }
     } else if (command == "info") {
         if (!fs::exists(path)) {
-            fprintf(stderr, "Error: no wallet file at %s\n", name.c_str());
+            tfm::format(std::cerr, "Error: no wallet file at %s\n",
+                        name.c_str());
             return false;
         }
         std::string error;
         if (!WalletBatch::VerifyEnvironment(path, error)) {
-            fprintf(
-                stderr,
+            tfm::format(
+                std::cerr,
                 "Error loading %s. Is wallet being used by other process?\n",
                 name.c_str());
             return false;
@@ -152,7 +158,7 @@
         WalletShowInfo(wallet_instance.get());
         wallet_instance->Flush();
     } else {
-        fprintf(stderr, "Invalid command: %s\n", command.c_str());
+        tfm::format(std::cerr, "Invalid command: %s\n", command.c_str());
         return false;
     }
 
diff --git a/test/lint/lint-format-strings.py b/test/lint/lint-format-strings.py
--- a/test/lint/lint-format-strings.py
+++ b/test/lint/lint-format-strings.py
@@ -19,7 +19,6 @@
     ("src/netbase.cpp", "LogConnectFailure(bool manual_connection, const char *fmt, const Args &... args)"),
     ("src/util/system.cpp",
      "strprintf(_(COPYRIGHT_HOLDERS), _(COPYRIGHT_HOLDERS_SUBSTITUTION))"),
-    ("src/seeder/main.cpp", "fprintf(stderr, help, argv[0])"),
     ("src/tinyformat.h", "printf(const char *fmt, const Args &... args)"),
     ("src/tinyformat.h", "printf(const char *fmt, TINYFORMAT_VARARGS(n))"),
     ("src/wallet/wallet.h",
@@ -37,6 +36,7 @@
     ("snprintf", 2),
     ("sprintf", 1),
     ("strprintf", 0),
+    ("tfm::format", 1),  # Assuming tfm::::format(std::ostream&, ...
     ("vfprintf", 1),
     ("vprintf", 1),
     ("vsnprintf", 1),