Unix/Linux/Windows systems uses PATH variable to look up the standard bin files of the inbuilt command in the Shell...This PATH variable can be changed and thus we can change the flow of a program using system() call...How? This we'll be seeing in this tutorial.. Method We'll be using a basic C Program for demonstarting our article.. system.c Code: #include<stdio.h> int main() { system("ls"); return(0); } Compiling Code: gcc system.c -o system Running Code: aneesh@aneesh-laptop:~/articles/C$ ./.system buggyProgram format getSrc stack2 stack.c system.c test buggyProgram.c format.c stack stack2.c system system.x test.c lets echo the PATH variable and know what it contains Code: aneesh@aneesh-laptop:~$ echo $PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games This means that the each command we enter into the shell is searched in the above PATH's.. So lets change it and add our own path at the beginning.. Code: aneesh@aneesh-laptop:~$ PATH=$HOME/articles:$PATH We added $HOME/article at the beginning of the path variable... Now lets add a program named 'ls' in the $HOME/articles directory... Code: aneesh@aneesh-laptop:~$ cd $HOME/articles ls.c Code: #include<stdio.h> int main() { printf("Hello World!!\n"); return(0); } Compiling Code: gcc ls.c -o ls Now that we have a file named 'ls' and the PATH variable Changed. So , now we are ready to exploit the system.c program... Lets run it now... Code: aneesh@aneesh-laptop:~/articles/C$ ./system Hello World!! Yupi!!!We did it again...We just exploited the system.c program to change its normal Program Flow..
Sorry cant understand your question fully but i am assuming that you wanted to ask...What is C and how to program in C... C is a Powerful Programming Language... It was made in late 1970's by Dennis Ritchie and Bell Labs for the Unix systems... It gained a lot of popularity and till today also is one of the most popular programming language... Programming in C is a long journey but full of excitement and Interesting memory leaks !! () ... For more info Click Here!!
