diff --git a/.github/workflows/CI-unixish.yml b/.github/workflows/CI-unixish.yml
index 7a64ee14..3a604900 100644
--- a/.github/workflows/CI-unixish.yml
+++ b/.github/workflows/CI-unixish.yml
@@ -1,4 +1,4 @@
-name: CI Unixish
+name: CI-unixish
 
 on: [push, pull_request]
 
@@ -28,6 +28,10 @@ jobs:
     - name: make test
       run: make -j$(nproc) test CXX=${{ matrix.compiler }}
 
+    - name: selfcheck
+      run: |
+        make -j$(nproc) selfcheck CXX=${{ matrix.compiler }}
+
     - name: Run valgrind
       if: matrix.os == 'ubuntu-22.04'
       run: |
@@ -35,24 +39,25 @@ jobs:
           # this valgrind version doesn't support DWARF 5 yet
           make -j$(nproc) CXX=${{ matrix.compiler }} CXXFLAGS="-gdwarf-4"
           valgrind --leak-check=full --num-callers=50 --show-reachable=yes --track-origins=yes --gen-suppressions=all --error-exitcode=42 ./testrunner
+          valgrind --leak-check=full --num-callers=50 --show-reachable=yes --track-origins=yes --gen-suppressions=all --error-exitcode=42 ./simplecpp simplecpp.cpp -e
 
     - name: Run with libstdc++ debug mode
       if: matrix.os == 'ubuntu-22.04' && matrix.compiler == 'g++'
       run: |
         make clean
-        make -j$(nproc) test CXX=${{ matrix.compiler }} CXXFLAGS="-g3 -D_GLIBCXX_DEBUG"
+        make -j$(nproc) test selfcheck CXX=${{ matrix.compiler }} CXXFLAGS="-g3 -D_GLIBCXX_DEBUG"
 
     - name: Run with libc++ debug mode
       if: matrix.os == 'ubuntu-22.04' && matrix.compiler == 'clang++'
       run: |
         make clean
-        make -j$(nproc) test CXX=${{ matrix.compiler }} CXXFLAGS="-stdlib=libc++ -g3 -D_LIBCPP_ENABLE_ASSERTIONS=1" LDFLAGS="-lc++"
+        make -j$(nproc) test selfcheck CXX=${{ matrix.compiler }} CXXFLAGS="-stdlib=libc++ -g3 -D_LIBCPP_ENABLE_ASSERTIONS=1" LDFLAGS="-lc++"
 
     - name: Run AddressSanitizer
       if: matrix.os == 'ubuntu-22.04'
       run: |
         make clean
-        make -j$(nproc) test CXX=${{ matrix.compiler }} CXXFLAGS="-O2 -g3 -fsanitize=address" LDFLAGS="-fsanitize=address"
+        make -j$(nproc) test selfcheck CXX=${{ matrix.compiler }} CXXFLAGS="-O2 -g3 -fsanitize=address" LDFLAGS="-fsanitize=address"
       env:
         ASAN_OPTIONS: detect_stack_use_after_return=1
 
@@ -60,11 +65,11 @@ jobs:
       if: matrix.os == 'ubuntu-22.04'
       run: |
         make clean
-        make -j$(nproc) test CXX=${{ matrix.compiler }} CXXFLAGS="-O2 -g3 -fsanitize=undefined -fno-sanitize=signed-integer-overflow" LDFLAGS="-fsanitize=undefined -fno-sanitize=signed-integer-overflow"
+        make -j$(nproc) test selfcheck CXX=${{ matrix.compiler }} CXXFLAGS="-O2 -g3 -fsanitize=undefined -fno-sanitize=signed-integer-overflow" LDFLAGS="-fsanitize=undefined -fno-sanitize=signed-integer-overflow"
 
     # TODO: requires instrumented libc++
     - name: Run MemorySanitizer
       if: false && matrix.os == 'ubuntu-22.04' && matrix.compiler == 'clang++'
       run: |
         make clean
-        make -j$(nproc) test CXX=${{ matrix.compiler }} CXXFLAGS="-O2 -g3 -stdlib=libc++ -fsanitize=memory" LDFLAGS="-lc++ -fsanitize=memory"
+        make -j$(nproc) test selfcheck CXX=${{ matrix.compiler }} CXXFLAGS="-O2 -g3 -stdlib=libc++ -fsanitize=memory" LDFLAGS="-lc++ -fsanitize=memory"
diff --git a/.github/workflows/CI-windows.yml b/.github/workflows/CI-windows.yml
index aca68c93..1c4e3404 100644
--- a/.github/workflows/CI-windows.yml
+++ b/.github/workflows/CI-windows.yml
@@ -46,4 +46,8 @@ jobs:
       - name: Test
         run: |
           .\${{ matrix.config }}\testrunner.exe || exit /b !errorlevel!
+
+      - name: Selfcheck
+        run: |
+          .\${{ matrix.config }}\simplecpp.exe simplecpp.cpp -e || exit /b !errorlevel!
         
diff --git a/Makefile b/Makefile
index a209666e..db1ca257 100644
--- a/Makefile
+++ b/Makefile
@@ -16,6 +16,9 @@ test:	testrunner	simplecpp
 	./testrunner
 	python3 run-tests.py
 
+selfcheck:	simplecpp
+	./selfcheck.sh
+
 simplecpp:	main.o simplecpp.o
 	$(CXX) $(LDFLAGS) main.o simplecpp.o -o simplecpp
 
diff --git a/appveyor.yml b/appveyor.yml
index 00136602..ea8dd1df 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -17,3 +17,4 @@ build_script:
 
 test_script:
   - debug\testrunner.exe
+  - debug\simplecpp.exe simplecpp.cpp -e
diff --git a/main.cpp b/main.cpp
index 6592bf6c..7516085f 100644
--- a/main.cpp
+++ b/main.cpp
@@ -31,25 +31,34 @@ int main(int argc, char **argv)
     // Settings..
     simplecpp::DUI dui;
     bool quiet = false;
+    bool error_only = false;
     for (int i = 1; i < argc; i++) {
         const char * const arg = argv[i];
         if (*arg == '-') {
             bool found = false;
             const char c = arg[1];
-            const char * const value = arg[2] ? (argv[i] + 2) : argv[++i];
             switch (c) {
             case 'D': // define symbol
+            {
+                const char * const value = arg[2] ? (argv[i] + 2) : argv[++i];
                 dui.defines.push_back(value);
                 found = true;
                 break;
+            }
             case 'U': // undefine symbol
+            {
+                const char * const value = arg[2] ? (argv[i] + 2) : argv[++i];
                 dui.undefined.insert(value);
                 found = true;
                 break;
+            }
             case 'I': // include path
+            {
+                const char * const value = arg[2] ? (argv[i] + 2) : argv[++i];
                 dui.includePaths.push_back(value);
                 found = true;
                 break;
+            }
             case 'i':
                 if (std::strncmp(arg, "-include=",9)==0) {
                     dui.includes.push_back(arg+9);
@@ -70,11 +79,18 @@ int main(int argc, char **argv)
                 quiet = true;
                 found = true;
                 break;
+            case 'e':
+                error_only = true;
+                found = true;
+                break;
             }
             if (!found) {
-                std::cout << "Option '" << arg << "' is unknown." << std::endl;
+                std::cout << "error: option '" << arg << "' is unknown." << std::endl;
                 error = true;
             }
+        } else if (filename) {
+            std::cout << "error: multiple filenames specified" << std::endl;
+            std::exit(1);
         } else {
             filename = arg;
         }
@@ -83,6 +99,11 @@ int main(int argc, char **argv)
     if (error)
         std::exit(1);
 
+    if (quiet && error_only) {
+        std::cout << "error: -e cannot be used in conjunction with -q" << std::endl;
+        std::exit(1);
+    }
+
     if (!filename) {
         std::cout << "Syntax:" << std::endl;
         std::cout << "simplecpp [options] filename" << std::endl;
@@ -93,6 +114,7 @@ int main(int argc, char **argv)
         std::cout << "  -std=STD        Specify standard." << std::endl;
         std::cout << "  -q              Quiet mode (no output)." << std::endl;
         std::cout << "  -is             Use std::istream interface." << std::endl;
+        std::cout << "  -e              Output errors only." << std::endl;
         std::exit(0);
     }
 
@@ -102,6 +124,10 @@ int main(int argc, char **argv)
     simplecpp::TokenList *rawtokens;
     if (use_istream) {
         std::ifstream f(filename);
+        if (!f.is_open()) {
+            std::cout << "error: could not open file '" << filename << "'" << std::endl;
+            std::exit(1);
+        }
         rawtokens = new simplecpp::TokenList(f, files,filename,&outputList);
     }
     else {
@@ -118,7 +144,8 @@ int main(int argc, char **argv)
 
     // Output
     if (!quiet) {
-        std::cout << outputTokens.stringify() << std::endl;
+        if (!error_only)
+            std::cout << outputTokens.stringify() << std::endl;
 
         for (const simplecpp::Output &output : outputList) {
             std::cerr << output.location.file() << ':' << output.location.line << ": ";
diff --git a/selfcheck.sh b/selfcheck.sh
new file mode 100755
index 00000000..3518c654
--- /dev/null
+++ b/selfcheck.sh
@@ -0,0 +1,6 @@
+#!/bin/sh
+
+output=$(./simplecpp simplecpp.cpp -e 2>&1)
+ec=$?
+echo "$output" | grep -v 'Header not found: <'
+exit $ec
\ No newline at end of file