How to store a string

Variable type

1. const char *
2. char [] (can either specify size or not)

The main difference is that, const char * is not possible to be modified further. (i.e., an immutable string).

Given value

The value assigned can either be a

• string literal (ex: “Hello”, and C would automatically add ‘\0’ at the end)
• an array of characters (ex: {‘H’,’e’,’l’,’l’,’o’, ‘\0’})

const char* str1 = "Hello";
char str2[6] = "Hello";
char str3[6] = {'H', 'e', 'l', 'l', 'o'};

Manual copy

Shallow copy

char str1[] = "test";
char* str2 = str1;  //shallow copy

//modify str2
str2[0] = "T";

//check result
printf(str1);  //Test, also modified
printf("\n");
printf(str2);  //Test

Deep copy

char str1[5] = "test";
char str2[5];

for(int i=0;i<5;i++){
    str2[i] = str1[i];  //Deep copy
}

Use Function to copy

From string.h - strcpy. This would Deep Copy!

char * strcpy (char * destination, const char * source);
//copy source to destination

Note that, although the function specifies that destination of type char*, directly declare it as this type is invalid. (Reason: destination is going to be modified.)

Hence, destination should be of type char [] or char * s = malloc(...), so that actual memory space is allocated to it, and thus able to be modified.

const char* source = "test";

char * destination1 = NULL; 
char destination2[5];
char * destination3 = malloc(sizeof(char)*(strlen(source)+1));

strcpy(destination1, source);  //(x) compile error
strcpy(destination2, source);  //(o)
strcpy(destination3, source);  //(o)

return 0;