Mounting an ISO in FreeBSD

Mounting an ISO file in FreeBSD is slightly different than in Linux

In FreeBSD:

# mdconfig -a -t vnode -f  -u 0

mdconfig creates a memory disk /dev/md0. Then you mount it to your destination:

# mount -t cd9660 /dev/md0 

UnInheritable Class

You must be familiar with the NonCopyable Base class:


class NonCopyable
{
  protected:
    NonCopyable () {}
    ~NonCopyable () {}
  private: 
    NonCopyable (const NonCopyable&);
    NonCopyable& operator = (const NonCopyable &);
};

class A : private NonCopyable
{
};


How do you make a class un-inheritable?


template
class UnInheritable
{
private:
    ~NonInheritable();
    friend class T;
};


class A : virtual public UnInheritable
{
...
};

Slow SSH logon

If the hostname of a Linux box is not resolvable using DNS, SSH logins may be slow. It takes a several seconds from the Username prompt to Password prompt.

To resolve this problem edit

$ vi /etc/ssh/sshd_config
UseDNS no

# service ssh restart

Validate IPv4 netmask in C

Here's a useful routine I frequently use to validate whether a given string is a netmask or not:

int isValidNetMask (char* netmaskStr)
{
    unsigned char oneFound = 0;
    unsigned long int netmask = inet_addr(netmaskStr);
    
    if ( netmask == INADDR_NONE )
    {
        if ( strcmp(netmaskStr, "255.255.255.255") == 0 )
        {
            return 1;
        }
        return -1;
    }
    else
    {
        netmask = ntohl(netmask);
        unsigned long int mask;
        for ( mask = 1; mask; mask <<= 1 )
        {
            if ( netmask & mask )
            {
                oneFound++;
            }
            else if ( oneFound )
            {
                return -1;
            }
        }
        return 1;
    }
}

Acetaminophen Dosage for Infants and Children

Baby's Weight	Milligram Dosage	Infant Drops (80mg/0.8mL)	Children's liquid (160mg/5mL)
5-8 lbs	40mg	½ dropper	¼ tsp
		(.4ml)	(1.25ml)
9-10 lbs	60mg	¾ dropper	1/3 tsp
		(.6ml)	(1.8ml)
11-16 lbs	80mg	1 dropper	½ tsp
		(.8ml)	(2.5ml)
17-21 lbs	120mg	1 ½ droppers	¾ tsp
		(1.2ml)	(3.75ml)
22-26 lbs	160mg	2 droppers	1 tsp
		(1.6ml)	(5ml)
27-32 lbs	200mg	2 ½ dropper	1 ¼ tsp
		(2ml)	(6.25ml)
33-37 lbs	240mg	3 droppers	1 ½ tsp
		(2.4ml)	(7.5ml)
38-42 lbs	280mg	3 ½ droppers	1 ¾ tsp
		(2.8ml)	(8.75ml)
43-53 lbs	320mg	4 droppers	2 tsp
		(3.2ml)	(10ml)
54-64 lbs	400mg	Use Liquid	2 ½
			tsp(12.5ml)
65-75 lbs	480mg		3 tsp
			(15ml)
76-86 lbs	560mg		3 ½ tsp
			(17.5ml)
87-95 lbs	640mg		4 tsp
			(20ml)

Milky Way over Nepal

Photo by Anton Jankovoy

Unix and C were pranks!

Thompson, Ritchie and Kernighan admit that Unix was a prank. Interesting read!