MacBookAir:~ nagasm$ ls Applications Downloads Music a.out Desktop Library Pictures hello.c Documents Movies Public MacBookAir:~ nagasm$ gcc hello.c ld: can't write output file: a.out for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) MacBookAir:~ nagasm$ ls Applications Downloads Music a.out Desktop Library Pictures hello.c Documents Movies Public MacBookAir:~ nagasm$ gcc -v Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1 Apple LLVM version 7.0.0 (clang-700.1.76) Target: x86_64-apple-darwin14.5.0 Thread model: posix MacBookAir:~ nagasm$ gcc -o hello hello.c MacBookAir:~ nagasm$ ls Applications Downloads Music a.out Desktop Library Pictures hello Documents Movies Public hello.c MacBookAir:~ nagasm$ ./hello Hello, world! MacBookAir:~ nagasm$ cat hello.c #include int main(int argc, char *args[]) { printf("Hello, world!\n"); return 0; } MacBookAir:~ nagasm$