Very Computer

Dear all,

I was trying to implement some code samples found in R.Stevens's bible. I
need some memory shared between parent and a child, and was hoping to get
away with mmap(), using either MAP_ANON flag or using open file handle
/dev/zero.

There is a piece of code ( I'm omitting any error control):
{
    int file;
    caddr_t pvAllocation;

    file = open( "/dev/zero",
                      O_RDWR);

    pvAllocation = mmap(  0,
                                        cbAllocationSize,
                                        PROT_READ | PROT_WRITE,
                                        MAP_SHARED,
                                        file,
                                        0);

    pvAllocation = mmap(  0,
                                        cbAllocationSize,
                                        PROT_READ | PROT_WRITE,
                                        MAP_SHARED | MAP_ANON,
                                        -1,
                                        0);

    close( file);

Quote:}

In both cases pvAllocation is returned as -1, and errno is set no EINVAL
 0x16).
file gets a valid descriptor number.

Any help will be highly appreciated.

Thank you,
Ilya