Tag Archives: c

C program to get mac address from interface name on Linux

By | September 11, 2012

The mac address or the hardware address or the ethernet address of an interface is a 48 bit number that looks like this : 00:1c:c0:f8:79:ee The mac address of an interface can be found given its name. The function to use is ioctl. Code #include <stdio.h> //printf #include <string.h> //strncpy #include <sys/socket.h> #include <sys/ioctl.h> #include… Read More »

C program to get ip address from interface name on Linux

By | March 17, 2012

Interface name is something like “eth0” and the ip address of the interface can be retrieved using the ioctl function. Here is a simple piece of code that demonstrates how : Code #include <stdio.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <sys/ioctl.h> #include <netinet/in.h> #include <net/if.h> #include <unistd.h> #include <arpa/inet.h> int main() { int fd;… Read More »

Get time difference in microtime in C

By | March 9, 2012

The function gettimeofday can be used to retrieve the total number of seconds and balance microseconds elapsed since EPOCH. Structure timeval looks like this : struct timeval { time_t tv_sec; /* seconds */ suseconds_t tv_usec; /* microseconds */ }; On Linux it can be done like this : /** * Get time difference in microseconds… Read More »

C code to perform IP whois

By | September 21, 2012

Theory The whois information of an ip address provides various details like its network, range, isp etc. This information is maintained by various regional registry servers. Read the wikipedia article on regional internet registries for more information. There are a total of 5 regional registries spanning various geographical regions of the world. For example if… Read More »

C program to get a domain’s whois information using sockets on Linux

By | November 28, 2012

Whois A whois client is a program that will simply fetch the whois information for a domain/ip address from the whois servers. The code over here works according to the algorithm discussed here. Code /* * @brief * Whois client program * * @details * This program shall perform whois for a domain and get… Read More »

str_replace for C

By | December 22, 2011

Php has a useful function called str_replace which can search and replace a certain string in another big string. However there is no such function in C. So I wrote up one for myself. Here is the code. /* * Search and replace a string with another string , in a string * */ char… Read More »

Get local ip in C on linux

By | March 6, 2013

Local Ip address The local ip is the source ip in IP packets send out from a system. When the system is a part of a local area network then the local ip in most cases is something like 192.168.*.* . The network interface (eth0) is assigned an ip address of that range. However when… Read More »