Shell bindings for C functions - an example

my_library_function.c

#include <my_library.h>

int
main (int argc, char *argv[])
{
    // Capture stdout file descriptor and position
    int orig_stdout_fd;
    fpos_t orig_stdout_pos;
    fflush (stdout);
    dup2 (fileno (stdout), orig_stdout_fd);
    fgetpos (stdout, &orig_stdout_pos);
    
    // Redirect what would normally go to stdout to go to stderr
    dup2 (fileno (stderr), fileno (stdout));
    
    // Run the function and get the result
    int result = my_library_function (1, 2, 3);
    
    // Restore stdout file descriptor and position
    fflush (stdout);
    dup2 (orig_stdout_fd, fileno (stdout));
    fsetpos (stdout, &orig_stdout_pos);
    close (orig_stdout_fd);
    
    // Serialize result and send to stdout
    fprintf (stdout, "%i", result);
    fflush (stdout);
    
    return 0;
}