There is no purely MATLAB code equivalent for this. You could probably use file I/O functions in C to check if the file exists (does opening the file succeed?) See the section on External Code Integration for how to call C or C++ functions from your MATLAB code. See in particular the examples on the documentation page for coder.ceval for how to call MATLAB code when you're not generating code and C code when you are.
I think you could substitute scanf in C. Alternately you could parse the char vector yourself and use str2double to turn character vectors representing numbers into numbers.
There is no purely MATLAB code equivalent for this. Any such MATLAB equivalent you would write would likely be quite complicated, unless you targeted it solely at the portion of the regular expression language you were using.
There is no purely MATLAB code equivalent for this. C has the capability to create directories.
I'm not sure C really has the concept of a current directory, so you're probably going to need to rethink this.
While this is in MATLAB code, C doesn't have the concept of a MATLAB search path. You're going to need to rethink this.
Consider str2double instead.
There is no purely MATLAB code equivalent for this. Just have your application exit.
You could write a set membership function that loops through the two vectors, but you would need to write that.
This is MATLAB code, but I think how to convert it would depend on what you're doing with those cells.
This could probably be done via a loop, but again what are you planning to do with those cells or with that string array?
As for your question "Do you think if it is possible for me to get the Matlab code of the above functions?" most of those are not implemented using MATLAB code. For those that are, the solution is unlikely to be as simple as copying the text of those functions in place of the function calls in your application.