Mounting an ISO with sys/mount.h

Question

I'm trying to mount an ISO file in a C++ program in linux

I'm aware of the linux command to achieve this, i.e mount -o loop ~/Test.iso /mnt/myISO

But the mount(2) man page states the following prototype for mounting :

int mount(const char *source, const char *target,
const char *filesystemtype, unsigned long mountflags,
const void *data);

How do I specify the loop option here ?

--

Also, is it good (/acceptable) practice in general, in linux programming to use system shell calls from C++ to achieve tasks such as these ?

Answer 1

small example

#include <sys/mount.h>
#include <linux/loop.h>
#include <fcntl.h>

int main()
{
    int file_fd, device_fd;

    file_fd = open("./TVM_TOMI1.iso", O_RDWR);
    if (file_fd < -1) {
        perror("open backing file failed");
        return 1;
    }
    device_fd = open("/dev/loop0", O_RDWR);
    if (device_fd < -1) {
        perror("open loop device failed");
        close(file_fd);
        return 1;
    }
    if (ioctl(device_fd, LOOP_SET_FD, file_fd) < 0) {
        perror("ioctl LOOP_SET_FD failed");
        close(file_fd);
        close(device_fd);
        return 1;
    }
    close(file_fd);
    close(device_fd);
    mount("/dev/loop0","/mnt/iso","iso9660",MS_RDONLY,"");
}

upd: after unmount you need free loop:

device_fd = open("/dev/loop0", O_RDWR);
...
if (ioctl(device_fd, LOOP_CLR_FD, 0) < 0) {
    perror("ioctl LOOP_CLR_FD failed");
    return 1;
}