Question

I’m writing a C app that has an embedded lua script in it. The Lua script takes input from STDIN. So when I’m running the script from the shell it’s like thus:

lua myscript.lua < datafile*

How do I accomplish this from inside the C code?

Thank you.

Answer 1

Use the dup2(2) system call on descriptor 0 (stdin) and on the descriptor returned by open(2) on datafile:

int fd = open("datafile", O_RDONLY);
dup2(fd, 0);
/* reading from stdin now is in fact reading from datafile */

Of course, you need some error-checking in a real-world program.

To implement the behaviour of wildcarding, you may want to look at the readdir(3) library function.