Best way to create a C String

Question

I'm currently using

char *thisvar = "stringcontenthere";

to declare a string in C.

Is this the best way to declare a string in C?

And how about generating a C-String from C++-Strings?

Answer 1

In C it depends on how you'll use the string:

• named constant: your char* str = "string"; method is ok (but should be char const*)
• data to be passed to subfunction, but will not not used after the calling function returns:
  char str[] = "string";
• data that will be used after the function it is declared in exits: char* str = strdup("string");, and make sure it gets freed eventually.

if this doesnt cover it, try adding more detail to your answer.

Answer 2

It depends. For ASCII encoded strings see paragraphs C and C++. For unicode encoded strings see last paragraph.

C:

As David pointed out it depends on how to use the string in C:

• as a constant then: const char s[] = "Hello World";
• as a string containing variable data then: char s[] = "Hello World";
• as a data array char *data; Initialization then should be customized.

Please note in C there are all Strings Null-terminated, that means the definition of e.g. char s[] = "foo"; implicitly includes a NULL character at the end s[3]='\0'.

Also please note the subtile difference between char *s and char s[] which might often behave the same but sometimes not! (see Is an array name a pointer?) for example:

#include <stdio.h>
#include <stdlib.h>

int main( int argc, char* argv[])
{
  char s[] = "123456789123456789123456789";
  char *t = (char*) malloc( sizeof(char) * 28 );
  for( size_t i = 0; i < 28; ++i )
      t[ i ] = 'j';
  printf( "%lu\n", sizeof(s) );
  printf( "%lu\n", sizeof(t) );
  printf( "%s\n", s );
  printf( "%s\n", t );
  return EXIT_SUCCESS;
}

So I recommend to use char arrays whenever you use them as strings and char pointers whenever you use them as data array.

C++:

In C++ there is an own string data type: std::string. If you just need to have a C-String version of a std::string (e.g. using some C-API) just use the c_str() member:

std::string s = "Hello World";
your_c_call( s.c_str(), ... );

Unicode:

I you want to have unicode strings then you should really go with something like

char utf8String[] = u8"Hello World";

and try not to use wchar_t whenever possible. See this excellent article on that issue: http://www.nubaria.com/en/blog/?p=289. Please not that there is also unicode support for C++. But generally I am tempted to say that you should go with normal characters as far as you can. Interesting resource on that: http://www.cprogramming.com/tutorial/unicode.html

Answer 3

const char *thisvar="stringcontenthere";

Answer 4

As other suggested, and I you want to "do it" the C++ way, use a std::string.

If you somehow need a C-string, std::string has a method that gives a const char*.

Here is an example:

#include <iostream>
#include <string>

void dummyFunction(const char* str)
{
  // Do something
}

int main(int, char**)
{
  std::string str = "hello world!";

  dummyFunction(str.c_str());

  return EXIT_SUCCESS;
}

Answer 5

Is this C or C++? In C++ you should use std::string:

std::string aString("stringcontenthere");