CODEWITHSUNDEEP
c++cstring
Daniel
Daniel

Reputation: 3077

Best way to create a C String

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?

Upvotes: 11

Views: 30084

Answers (5)

David X
David X

Reputation: 4166

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.

Upvotes: 16

math
math

Reputation: 8818

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

Upvotes: 1

Kamran Khan
Kamran Khan

Reputation: 9986

const char *thisvar="stringcontenthere";

Upvotes: 1

ereOn
ereOn

Reputation: 55726

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;
}

Upvotes: 1

P&#233;ter T&#246;r&#246;k
P&#233;ter T&#246;r&#246;k

Reputation: 116246

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

std::string aString("stringcontenthere");

Upvotes: 0

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