How to create one array of char from different variable(data type) in one line?

Question

Is it possible to create array of char from different data types merging it into one char array. char array[32] = "matrix"+a+b+".txt"; E.g:

int main(){
int a = 10;
int b = 10;

char array[32] = "matrix"+a+b+".txt";
return 0;
}

I have tried different ways. But it didn't helped. Thank you!

It is better for c. Also, it will be great if you will give for c++. — Jasurbek Nabijonov, Apr 14 '17 at 18:45
In c++ [`std::string`](http://en.cppreference.com/w/cpp/string/basic_string) will do that for you. It overloads `operator+`. See [`std::to_string`](http://en.cppreference.com/w/cpp/string/basic_string/to_string) for converting `int` to `std::string`. — François Andrieux, Apr 14 '17 at 18:45
@JasurbekNabijonov This is why everyone wants you to specify 1 language. The solutions aren't remotely similar. You are asking two different questions in the same post. — François Andrieux, Apr 14 '17 at 18:47

cdhowie · Accepted Answer · 2017-04-14T18:48:42.513

3

For C, use snprintf():

int a = 10;
int b = 10;

char array[32];

snprintf(array, sizeof(array), "matrix%d%d.txt", a, b);

For C++, use strings instead of character arrays; you can concatenate strings easily since they overload the + operator:

int a = 10;
int b = 10;

std::string str{std::string{"matrix"} + std::to_string(a) + std::to_string(b) + ".txt"};

edited Apr 14 '17 at 18:48

answered Apr 14 '17 at 18:46

cdhowie

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Wow! It works great! Thank you very much! – Jasurbek Nabijonov Apr 14 '17 at 18:48

Wagner Patriota · Answer 2 · 2017-04-14T18:58:30.647

I think you should firstly understand how a C-string works... a C-String is always an array of chars... but an array of char is not always a C-String.

The "definition" (not a formal definition, but something close to it) is that a C-String contains a sequence of bytes that will represent a string (characters) and the end of the string will be marked with a null-byte (0)

This is a C-String:

char myString[4] = { 'a', 'b', 'c', 0 };

This is NOT a C-String:

char myBuffer[3] = { 'a', 'b', 'c' };

Checking your example... trying to make "matrix"+a+b+".txt" shows that you are actually looking for construct a C-String with different types.

--

So, in order to mix different types of data in order to build a string we have several options...

In C: use snprintf()
In C++: use std:string or std::ostringstream

There are more options for both, but these above are very common.

The std::string in C++ is NOT a C-String... but can be converted to one with the function .c_str().

How to create one array of char from different variable(data type) in one line?

2 Answers2