Windows和Linux中的printf之间的区别

Question

Actually other than the core C language, there is a C library. And if my understanding is right, functions like printf are part of C library. Now I have programmed in C in Turbo C in Windows as well as using gcc in Linux.

My question is: Are the code implementations of functions like printf the same in both Windows and Linux? Ultimately the printf function has to call a function in core OS (in both cases) that would display ASCII characters onto the screen? So since both the OS are different, will the implementation of code for printf be also different in both the cases?

Answer 1

Of course the implementation (of printf and all functions in <stdio.h> ) is different (on Linux and on Windows), but the behavior should be conforming to the specification in the C11 or C99 standard.

Notice that printf does not show characters on the screen, but send them to the standard output (see printf(3) ). Something else -eg the kernel tty layer and your terminal emulator on Linux- is displaying the characters on your screen (or elsewhere!).

On Linux and POSIX systems, <stdio.h> is ultimately using system calls to write data to a file descriptor . It would be write(2) (for printf ) and the list of system calls is available in syscalls(2) . Be aware that stdout is usually buffered (notably for performance reasons; making a write syscall for every written byte would be too costly). See fflush(3) & setvbuf(3) . Try using strace(1) on your Linux program to understand the actually used syscalls.

On Windows, there is some equivalent thing (except that the list of syscalls on Windows is less documented and is very different).

BTW, GNU/Linux is mostly free software . So read Advanced Linux Programming then study the source code: the libc is often glibc (but could be musl-libc , etc... so you can have several implementations of printf on Linux, but usually you have one libc.so , even if you could have several ones), the kernel source is available on kernel.org .