I was reading "The C Programming Language" by Kernighan & Ritchie and came across some programs which mimic some Unix commands (also implemented in Linux) such as the cat command. The program took command line arguments just like the original cat command.
I am just curious to know whether they are the same thing or not.
Correct me if I'm wrong, any help would be appreciated.
In a command-line environment (such as, of course, Unix/Linux), a principle unit of abstraction is the command. A command has a well-defined interface: the command-line arguments it expects, the input it reads (if any), and the output it generates. You can reimplement a command any time you like, either using a different internal algorithm, or a different language, or just because you want to write your own version. Yes, cat was originally written in C, but we could rewrite it in C++, or Perl, or Python, or sh, or other languages. As long as our reimplementation meets the same interface requirements, we can accurately say that it "is" cat.