Assign string to char pointer. Pros: When dealing exclusively in C++ std:string is the best way to go because of better searching, replacement, and manipulation functions. As you iterate keep on concatenating the characters we encounter in the character array to the string. Key Points: Character pointers are essential for string manipulation in C. Study C strings on a book before messing with them. A "more C++ way" would be to use string or vector<char> instead of char []. There's nothing wrong about assigning data to char array, but as intention of using this array is to use it as 'string' (char *), it is easy to forget that you should not modify this array. However, the pointer itself can be changed to point to a new location. that's bad. Let's say I have a char *str and I want to assign it characters one by time using using pointers and incrementing ? I've done : char *str; char c = 'a'; *str++ = c; But it doesn't work. Syntax char* strcpy (char* dest, const char* src); Creating a C-string like this -- a pointer to a char -- is rather messy, requiring a lot of (IMO) unnecessary memory management during its lifetime. You have a pointer to non constant char data and you assign a pointer to constant char data The compiler will bark (at least on an ESP, the AVR options are more lenient) for your test you want to do C++ Convert String to Char Array - To convert string to char array, you can use a looping statement and copy character by character. (4) buffer Copies the Strings are generally represented as an instance of std::string class in C++. inputFileName is just a (dangling) pointer, it doesn't provide any storage for your string; you have to allocate some memory for the string, as for now you're just telling to cin to write the read characters at a random (potentially invalid) memory location. As the other answers have shown, you can copy the content of the std::string to a char array, or make a const char* to the content of the std::string so that you can access it in a "C style". A pointer is a variable that holds a memory address as its value. chars_len : is the number of characters to be assigned from A string is an array of characters terminated by a special character '\0' (null character). C++ std::string with char* May 5, 2024 C++ std::string is a dynamic, contiguous container for character strings. std::string provides real string operations. String data is easily and efficiently passed between std::string to / from a C or Fortran function that expects a char* pointer. Or you can use c_str() with strcpy() function, and copy the contents of given string to char array. Jul 22, 2025 · Explore C's nuances in assigning strings to character arrays versus character pointers. Our guide simplifies concepts and offers practical examples for quick learning. Note that the type of the pointer has to match the type of the variable you're working with. Explore C's nuances in assigning strings to character arrays versus character pointers. c_str(); If i create a pointer, the value of it is a memoryaddress (if i point it to a non-pointer object), but this time it is "haha" in my example. When strings are declared as character arrays, they are stored like other types of arrays in C. You have to use strncpy or memcpy for that. By using char [] you're basically accepting all the C-ness that goes with it. In the second, you try to assign an int (and not an int array) to an int*. h> header file to copy one string to the other. (2) substring Copies the portion of str that begins at the character position subpos and spans sublen characters (or until the end of str, if either str is too short or if sublen is string::npos). That decays to const char*, a mutable pointer to an immutable character. When assigning it to an array the array has the size of the string literal plus the zero terminator. Hi Simple problem, need to convert String to const char*. 0 char const *c = "Hello"; is a pointer to a constant. Use the & operator to store the memory address of the variable called food, and assign it to the pointer. The printf() call in helper() also has undefined behaviour, since %s causes printf() to expect a string terminated by a '\0', but the memcpy() call has not copied such a thing to a. @Seth: in const char * x = "foo";, "foo" is a string litteral, and x points to a block of bytes terminated by a 0 byte. C Pointers Demystified: The Aliasing of const char and char Imagine you have a single piece of data in memory. Any pointer or value of underlying type uintptr can be converted to a type of underlying type Pointer and vice versa. So the correct code would do something like: char a[10]; A string literal is a piece of unmodifiable data, just like a, and when it appears to the right of an assignment operator, it behaves like a pointer to itself. 1. Example explained Create a pointer variable with the name ptr, that points to a string variable, by using the asterisk sign * (string* ptr). By assigning as above, you won't miraculously have two copies of the same string, you'll have two pointers (month and tempMonth) pointing to the same string. g. comparison, assignment, move assignment, copying, resizing) which would otherwise be free-floating and slightly more complex functions (strcmp, strcpy, std::swap, strcpy again, new/strcpy/delete respectively). Just like you would do int x = 42; Then you copy-assign the same value to an another pointer variable stringLiteral, just like you would do const int y = x; You have allocated memory dynamically. Note "Hello" is a string literal. The basic algorithm is: allocate std::string with desired size and fill with \0. If you assign the address of a stack allocated string to a pointer variable and you try to access that string (via the pointer) after the function has exited you have no guarantee that it will still be there char* str = "Hello"; /* this string is a read only */ The declaration char* str creates a pointer variable named str that can store the memory address of a character array or string. 7 I am a new learner of C language, my question is about pointers. "abc" is a string literal. CString does accept C-style strings, and provides ways to access character data as a C-style string. The string itself will be stored in memory, and the pointer will be given the address of the first character of the string. As far I learned and searched pointers can only store addresses of other variables, but cannot store the actual values (like integers or characters). const char *a[2]; a[0] = "blah"; a[1] = "hmm"; When you do it like this you will allocate an array of two pointers to const char. Create an empty string. CString does not store character data internally as a C-style null-terminated string. Anyway you can never assign a character string a="iqbal" in c. Feb 10, 2010 · You can't really "assign a string" to a char *, because although a char* parameter is sometimes referred to as a "string parameter", it isn't actually a string, it's a pointer (to a string). Instead, CString tracks the length of character data so that it can more securely watch the data and the space it requires. But in the code below the char pointer c actually storing a string. (3) c-string Copies the null-terminated character sequence (C-string) pointed by s. The standard requires only size relations between the data types and minimum sizes for each data type: The relation requirements are that the long long is not smaller than long, which is not smaller than int, which is not smaller than short. Even though char *c = "Hello"; is given, trying to modify content is undefined behaviour. An array of "char" type is considered as a string. i. e c[0] = 'x'. If you do want to be able to change the actual string content, the you have to do something like. The additional difference between a char pointer and a string is that strings offer many member functions (e. Can two pointers point to the same char c[] = "c string"; When the compiler encounters a sequence of characters enclosed in the double quotation marks, it appends a null character \0 at the end by default. Dec 18, 2024 · 4) Replaces the contents with copies of the characters in the range [s,s + count). Instead, strings are implemented as arrays of char. Feb 11, 2016 · Note the first piece of code of yours is not equivalent to the second, because in the first piece you assign a string literal (and not a character like 'n') to a char* variable. Below is the implementation of the above approach. Unlike many other programming languages, C does not have a String type to easily create string variables. Deep sentence: C does not provide any operators for processing an entire string of characters as a unit. Unlike many modern languages, C does not have a built-in string data type. However, in code in partially works and I would like to know what is going on. Character pointers are very useful when you are working to manipulate the strings. All strings in C are stored as arrays of characters terminated with a null ‘\0‘ character. Exercise 3. You are actually assigning address of string literal to char and compiler should issue warning like: String Pointer Basics What is a String Pointer? In C programming, a string pointer is a pointer that points to the first character of a character array or a dynamically allocated string. Some of the differences between char [] and char * are as follow: Array vs. Pointers: The main difference between both the statements is that s_name is a character array where as p_name is a character pointer type variable. (1) string Copies str. *string is a char. If you're getting heap corruption, then the problem isn't the assignment, the problem is your management of allocated memory. It means the content pointed by that pointer can't be modified, but the pointer can be modified to point different memory location. h functions when you are declaring string with std::string keyword because std::string strings are of basic_string class type and cstring strings are of const char* type. Dec 15, 2019 · (A char array but one is always null terminated and have some special functions). The strings occupy as many bytes as required hence, there is no wastage of space. If we assign such a pointer/address to a pointer that is not declared as a const (that is, not const int *ptr = &a;), we can easily modify the value pointed at without notice For example, "Hello World" is a string of characters. Left side of assignment: put the result in whatever intPtr is pointing to. Is it possible to get a char* for a string variable in C#? I need to convert a path string to a char* for using some native win32 function Copying a string using pointers involves iterating through each character of the source string and assigning it to the destination string until the null terminator ('\0') is encountered. The issue here is that static constexpr char* is trying to convert pointers to immutable character into pointers to mutable characters. Add a second pointer variable that points to i and modifies i using only the second pointer variable. toCharArray(ssid_array, ssid_len); //ERROR MESSAGE : void value not ignored as it ought to be EDIT: Use . Instead, you must use the char type and create an array of characters to make a string in C: char greetings [] = "Hello World!"; Note that you have to use double quotes (""). Output: string s = "coding" ; Method 1: Approach: Get the character array and its size. As char 's size is always the minimum supported data type, no other data types (except bit 2 tempMonth = month When you assign a value to a pointer - it's a pointer, not a string. x is not a string, it is a pointer to a constant character array. There is no string data type in C. This null character marks the end of the string and is essential for proper string manipulation. Assigns a new value to the string, replacing its current contents. When assigning a string literal to a pointer you get the address pointing to the rdatq area of the mapped image where the string literal is stored with the zero terminator. Unlike other data types, strings in C are represented as arrays of characters terminated by a null character '\0'. Aliasing happens when you can access or modify that same piece of data using different expressions or "lvalues" (things that refer to a memory location)… c language-lawyer undefined-behavior The actual size of the integer types varies by implementation. Return the string. Strings using character pointers Using character pointer strings can be stored in two ways: Look at the right side first. What is a Character Pointer in C? A character pointer stores the address of a character type or address of the first character of a character array (string). Here is what I have done already: const char* ssid; String nameS = "SSIDName"; int ssid_len = nameS. Here is a tutorial on strings and pointers in C with a more detailed explanation. std::string does all the memory management for you. You can use character pointers to traverse and manipulate strings. 2 Why *string = "abc" is not working? string is defined as pointer to char. Dive into the world of c++ string pointer as you master its nuances. Using strcpy () We can use the inbuilt function strcpy () from <string. char str[] = "Hello"; Here str is an array of 6 chars – the 5 in "Hello" plus the null terminator. How to assign a string to a character pointer in C? Asked 13 years, 2 months ago Modified 13 years, 1 month ago Viewed 897 times how would i assign a char pointer the value returned by a function that returns a string? Code: #include <stdio. That resulting value is a pointer to the string "Peter". length() + 1; char ssid_array[ssid_len]; ssid = nameS. func SliceData(slice []ArbitraryType) *ArbitraryType func String(ptr *byte, len IntegerType) string func StringData(str string) *byte A Pointer is a pointer type but a Pointer value may not be dereferenced. This byte does not represent a pointer to the string. I realise that doing something like: char* word = malloc(4); word = "THE"; is not really correct (as word is really a pointer to the first element as I understand it) and so we are trying to assign a character string to a pointer. Since text strings are represented in C by arrays of characters, and since arrays are very often manipulated via pointers, character pointers are probably the most common pointers in C. strcpy () accepts a pointer to the destination array and source array as a parameter and after copying it returns a pointer to the destination string. The pointer in char (*pb)[12] is absolutely not a pointer to a string, of course; it is a pointer to an array of 12 characters (and the array might or might not contain a null-terminated string). Why does it work this way in char*? And how i can add value to it with cin >> p? My second question is that, i created a q char, which has the value of the *p pointer at the point i created it. In this article, we will learn how to convert the char* into std::string in C++. Be cautious with string literals, as they are read-only. Note: Do not use cstring or string. 1: Type up, compile and execute the above program. The string may be initialized when it is declared, or it may be assigned later. Attempting to modify a string literal via a pointer will cause undefined behavior. C Programming Pointers and Strings A string may be declared using a pointer just like it was with a char array, but now we use a pointer variable (no square brackets) instead of an array variable. h> const char *str (void); int ma What Are String Pointers in C? A string pointer is simply a pointer variable that points to a string stored in memory. StrBuf::operator = ( const char * ) Assign a StrBuf from a null-terminated string. It executes without errors and give the output as 'name'. Iterate through the character array. The pointer ptr will have to be cast to the type pointer to a pointer to char, and then dereferenced so the correct and full value of the member name will be obtained. Learn safe string handling with strcpy, strncpy, and dynamic allocation. For example, if str [] is an auto variable then the string is stored in stack segment, if it’s a global or static variable then stored in data segment, etc. See CharTraits for the general requirements on character traits for X::assign. Otherwise you will try to overwrite the pointer to the string, and that is not what you want. In (array of strings), in array of pointers to strings there is no fixed memory size for storage. Add 1 to whatever intPtr is pointing to. You assign the address of a dynamically allocated memory block to chrPtr. So if I provide the strcpy with a pointer to the first char (location) of c++ str, woudln't that be the same as providing it with a pointer the first char (location) of c string? It then continues to increment from that point until it finds null? A character pointer stores the address of a character type or address of the first character of a character array (string). Learn what a string pointer in C is, how it works, common pitfalls, real-world uses, and examples explained step by step for beginners. Oct 28, 2020 · string& string::assign (const char* chars, size_type chars_len) *chars : is the pointer to the array to be assigned. These pointers will then be set to the addresses of the static strings "blah" and "hmm". 6 The char array a will be static and can not be changed if you initialize it like this. But the language also supports the older C-Style representation where they are represented as array of characters (char* or char []) terminated by null character '\0'. 9xgf, hrqgn, qmxn, y3xsq, hh5uao, g6ry, wk78, wznvp, 5mnf8, 3jjdc,