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Briefly: do NOT use C strings except for the most trivial tasks (constants). Use std::string instead, and convert (using c_str()) when needed. If you think I am exaggerating, you'll think again when your program will crash.

C Strings are nothing but C arrays of char values, with the added convention that a NUL ('\0') character signals the end of the string. For mysterious reasons, the authors of C did not give much thought to what happens if that NUL is missing, or if you try to copy a long string into a small one.

Note also that, because of this thing, the size of a C string and the length of it are two separate things: the first is the size of the array, sizeof(stringVar), the second is the position of the terminator, strlen(stringVar).

Some people seem to think that C strings are much more efficient than std::string. Well, no, the overhead of std::string is minimal. It's just the fact that using C strings is such a pain, that you are forced to think carefully at each step and you end up doing as little as possible with them. Which is obviously faster.

/*
* Containers: C String
*/

#include <iostream>
#include <cstring>

int main() {
// constructor, assignment
char cHeader1[]="x, f(x)";
cout<<cHeader1<<" (size="<<strlen(cHeader1)<<")\n";
/*
* header1 was built with the length of the initialization string,
* and the length cannot be increased. So you cannot append
* more stuff to it.
* What you can do is construct it with an explicit size,
* guessing how much should be enough.
*/
char cHeader[256]="x, f(x)";

/*
* assign a new value
*
* BEWARE, if you write
* header="X, f(x)";
* you will "lose" the old memory (leak),
* instead reference a new memory area
* which may be shorter...
*/
//cHeader="X, f(x)"; // may seem to work, but don't do it!!
/*
* do NOT use plain strcpy,it may overwrite memory
* beyond the string length
*/
strncpy(cHeader,"X, f(x)",sizeof(cHeader)-1);
cHeader[sizeof(cHeader)-1]='/0'; // make sure it's zero-terminated

/*
* Append text to the string
* Do NOT use plain strcat, it may overwrite memory
* beyond the string length
*/
strncat(cHeader,", f2(x)",sizeof(cHeader)-strlen(cHeader)-1);
cHeader[sizeof(cHeader)-1]='/0'; // make sure it's zero-terminated

cout<<cHeader<<endl;

/*
* comparison
* For the same reasons give above,
* you must not use strcmp even to compare the whole string,
* but always strncmp, like
* strncmp(string,"text",sizeof(string))
*/
if (strncmp(cHeader+3,"f(",2)==0) {
// replace, even with a string of different length
//header.replace(3,2,"Function("); // can't do this with C-string
cout<<"equal\n";
}
cout<<cHeader<<endl;

}

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