<stdio.h> and <iostream>

Hi!

I'm quite used to handling data with <iostream> library.

In <stdio.h> there is a function called sprintf() that writes formatted data to a string. Does anyone know if there is a similar function in <iostream>?

There's stringstreams, which do the same thing, but the <iostream> library doesn't have a concept of format strings per se.

OK thanks.

You can format your output to any stream (whether it is an iostream or a stringstream) using manipulators from <iomanip>. For example, if you want your number output in hexadecimal with at least eight characters you might use:

Code:

---

#include <iostream>
#include <iomanip>

int main()
{
    int val = 123456789;
    std::cout << "0x";
    std::cout << std::setw(8) << std::setfill('0');
    std::cout << std::hex << val << '\n';
}
// output:
// 0x075bcd15

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Note that if you're using C++ and not C, you should include <cstdio> instead of <stdio.h>, because sometimes <stdio.h> might be non-standard.

Quote:

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Originally Posted by YAPP

Note that if you're using C++ and not C, you should include <cstdio> instead of <stdio.h>, because sometimes <stdio.h> might be non-standard.

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Technically, <stdio.h> is standard in C++, so it will work on any standards-compliant compiler. It is deprecated, however, and you're right that you should use <cstdio> instead.

Quote:

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Originally Posted by Jpsarapuu

Hi!

I'm quite used to handling data with <iostream> library.

In <stdio.h> there is a function called sprintf() that writes formatted data to a string. Does anyone know if there is a similar function in <iostream>?

---

With regards to <stdio.h> and sprintf(), if you are not aware, you should be using snprintf() instead, as the 'n' means there is a parameter used to limit the max amount of characters written into the array. It's a more secure usage (though it doesn't prevent you from sticking in a MAX that is larger than your array).

But I am not aware of a C++ equivalent.

I'll take a stab at C++ suggestions: using setbuf() in <cstdio> to set up a buffer for writing re-direction, stringstream in <iostream>.

You may find this article on the topic helpful. It compares all the standard ways of converting numbers to strings, and gives advanatges and disadvantages of each.