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#undef NDEBUG
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <assert.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
char *do_mmap(char *path, int *fd, off_t *size)
{
int err;
struct stat st;
char *p;
*fd = open(path, O_RDWR);
assert(*fd >= 0);
err = fstat(*fd, &st);
assert(!err);
*size = st.st_size;
// fuse doesn't support writable + shared
p = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED, *fd, 0);
assert(p != MAP_FAILED);
return p;
}
int main(int argc, char *argv[])
{
int err, fd1, fd2;
char *p, *q;
off_t size;
ssize_t ssz;
err = link(argv[1], argv[2]);
assert(!err);
p = do_mmap(argv[1], &fd1, &size);
q = do_mmap(argv[2], &fd2, &size);
assert(!memcmp(p, q, size));
ssz = write(fd1, "a", 1);
assert(ssz == 1);
munmap(q, size);
// close(fd2);
system("cat f2");
assert(!memcmp(p, q, size));
ssz = write(fd2, "b", 1);
assert(ssz == 1);
assert(!memcmp(p, q, size));
return 0;
}
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