freemem -- Device

Device that indicates amount of memory that is free
/dev/freemem

/dev/freemem is the device from which you can read the system's free memory
at any  given moment.   It has  major device 0,  the same as  /dev/null and
/dev/cmos; and minor number 12.

This non-portable  device node is used exclusively  for tracking the amount
of  free memory  in the  system.   Its driver  recognizes the  system calls
open(), close(), read(), and ioctl(), but not write().

Example

The following program prints the amount of free memory in your system.

#include <fcntl.h>
#include <sys/null.h>
#include <stdlib.h>

main()
{
    FREEMEM freemem;
    int fm_fd;

    fm_fd = open("/dev/freemem", O_RDONLY);

    if (fm_fd >= 0) {
        ioctl (fm_fd, NLFREE, &freemem);
        close (fm_fd);
        printf ("Available memory: %d kilobytes\n", freemem.avail_mem);
        printf ("Free memory: %d kilobytes\n", freemem.free_mem);
    } else
        printf("Cannot open /dev/freemem\n");
}

See Also

device drivers,
hmon,
ioctl(),
null

© 2012 by Stephen A. Ness