get ip address of ppp0

I would parse the results coming back from popen("ifconfig");

    int gethostname(char *hostname, size_t size);

 It returns the name of the computer that your program is running on.

   
    struct hostent *gethostbyname(const char *name);

it returns a pointer to a struct hostent, the layout of which is as follows:

    struct hostent {
        char    *h_name;
        char    **h_aliases;
        int     h_addrtype;
        int     h_length;
        char    **h_addr_list;
    };
    #define h_addr h_addr_list[0]

 

And here are the descriptions of the fields in the struct hostent:


h_name -- Official name of the host.

h_aliases -- A NULL-terminated array of alternate names for the host.

h_addrtype -- The type of address being returned; usually AF_INET.

h_length -- The length of the address in bytes.

h_addr_list -- A zero-terminated array of network addresses for the host. Host addresses are in Network Byte Order.

h_addr -- The first address in h_addr_list.

All descriptions copied from http://www.ecst.csuchico.edu/~beej/guide/net/html/syscalls.html

The hostent structure [usually] contains IP addresses, not ethernet MAC addresses.

scn's example worked perfectly.

Sunny, I had tried doing that way already, but it was only returning 10.0.0.1, and not the external address as well (I realize h_addr_list is an array that can contain more than one IP, but it only had 10.0.0.1 in my case).

Brett, I was parsing the output of ifconfig before, but the program had to make assumptions on the location of the ifconfig.  I wanted it to be more flexible for running on different machines.

Thanks for the input everyone.

There's a nice way of doing it from a bash script I found recently:

INET_IP=`ifconfig ppp0 | grep inet | cut -d : -f 2 | cut -d \  -f 1`