declaration and initialization of string in c

stackoverflow.com › questions › 4083239 › proper-way-to-initialize-a-string-in-c

You're supposed to set it before using it. That's the only rule you have to follow to avoid undefined behaviour. Whether you initialise it at creation time or assign to it just before using it is not relevant.

Personally speaking, I prefer to never have variables set to unknown values myself so I'll usually do the first one unless it's set in close proximity (within a few lines).

In fact, with C99, where you don't have to declare locals at the tops of blocks any more, I'll generally defer creating it until it's needed, at which point it can be initialised as well.

Note that variables are given default values under certain circumstances (for example, if they're static storage duration such as being declared at file level, outside any function).

Local variables do not have this guarantee. So, if your second declaration above (char *str;) is inside a function, it may have rubbish in it and attempting to use it will invoke the afore-mentioned, dreaded, undefined behaviour.

The relevant part of the C99 standard 6.7.8/10:

If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static storage duration is not initialized explicitly, then:

if it has pointer type, it is initialized to a null pointer;

if it has arithmetic type, it is initialized to (positive or unsigned) zero;

if it is an aggregate, every member is initialized (recursively) according to these rules;

if it is a union, the first named member is initialized (recursively) according to these rules.

Answer from paxdiablo on Stack Overflow

GeeksforGeeks

geeksforgeeks.org › c language › strings-in-c

Strings in C - GeeksforGeeks

November 14, 2025 - Instead, strings are implemented as arrays of char. ... #include <stdio.h> int main() { // declaring and initializing a string char str[] = "Geeks"; // printing the string printf("The string is: %s\n", str); return 0; }

Unstop

unstop.com › home › blog › strings in c | initialization and string functions (+examples)

Strings In C | Initialization and String Functions (+Examples)

May 30, 2025 - The source string is initialized as "Welcome to stringsunstop." Then, the first ten characters are changed using the memset() function, and the result, i.e., "$$$$$$$$$$ stringsunstop," is printed on the output screen.

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Personally speaking, I prefer to never have variables set to unknown values myself so I'll usually do the first one unless it's set in close proximity (within a few lines).

In fact, with C99, where you don't have to declare locals at the tops of blocks any more, I'll generally defer creating it until it's needed, at which point it can be initialised as well.

Note that variables are given default values under certain circumstances (for example, if they're static storage duration such as being declared at file level, outside any function).

The relevant part of the C99 standard 6.7.8/10:

If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static storage duration is not initialized explicitly, then:

if it has pointer type, it is initialized to a null pointer;

if it has arithmetic type, it is initialized to (positive or unsigned) zero;

if it is an aggregate, every member is initialized (recursively) according to these rules;

if it is a union, the first named member is initialized (recursively) according to these rules.

2 of 11

I'm wonder, what is the proper way of initializing a string?

Well, since the second snippet defines an uninitialized pointer to string, I'd say the first one. :)

In general, if you want to play it safe, it's good to initialize to NULL all pointers; in this way, it's easy to spot problems derived from uninitialized pointers, since dereferencing a NULL pointer will yield a crash (actually, as far as the standard is concerned, it's undefined behavior, but on every machine I've seen it's a crash).

However, you should not confuse a NULL pointer to string with an empty string: a NULL pointer to string means that that pointer points to nothing, while an empty string is a "real", zero-length string (i.e. it contains just a NUL character).

char * str=NULL; /* NULL pointer to string - there's no string, just a pointer */
const char * str2 = ""; /* Pointer to a constant empty string */

char str3[] = "random text to reach 15 characters ;)"; /* String allocated (presumably on the stack) that contains some text */
*str3 = 0; /* str3 is emptied by putting a NUL in first position */

TutorialsPoint

tutorialspoint.com › what-is-a-string-declare-and-initialize-the-strings-in-c-language

What is a string? Declare and initialize the strings in C language

Refer to the declaration given below − · char stringname [size]; For example - char a[50]; a string of length 50 characters. The initialization is as follows − · Using single character constant − · char string[20] = { ‘H’, ‘i’, ‘l’, ‘l’, ‘s’ ,‘\0’} Using string ...

WsCube Tech

wscubetech.com › resources › c-programming › strings

Strings in C Programming (Define, Declare, Initialize, Examples)

August 29, 2025 - Learn how to define, declare, and initialize strings in C programming with clear examples. Understand the basics of working with strings in C. Read now!

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scaler.com › home › topics › c strings - declaring strings in c

C Strings | Declaring Strings in C - Scaler Topics

December 21, 2023 - Highlights: There are four methods of initializing a string in C: Assigning a string literal with size. Assigning a string literal without size. Assigning character by character with size.

Guru99

guru99.com › home › c programming › strings in c: how to declare & initialize a string variables in c

Strings in C: How to Declare & Initialize a String Variables in C

August 8, 2024 - char first_name[15] = "ANTHONY"; ... and the characters are enclosed in single quotation marks. ‘C’ also allows us to initialize a string variable without defining the size of the character array....

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Strings in C – String Initialization, Accessing & Displaying

March 10, 2024 - A string in C is essentially a ... as it denotes where the string stops in memory. Strings can be initialized directly by assigning a string literal to a char array....

W3Schools

w3schools.com › c › c_strings.php

C Strings

For example, "Hello World" is a string of characters. Unlike many other programming languages, C does not have a String type to easily create string variables. Instead, you must use the char type and create an array of characters to make a string in C:

Codecademy

codecademy.com › docs › strings

C | Strings | Codecademy

April 21, 2025 - Master Python while learning data structures, algorithms, and more! ... Strings in C are declared using the char data type, followed by the string name and square brackets []. String values can be initialized in two ...

Programiz

programiz.com › c-programming › c-strings

Strings in C (With Examples)

... In C programming, a string is a sequence of characters terminated with a null character \0. For example: ... 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.

StudyRaid

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String declaration and initialization - C Programming Fundamentals: From Basics to File Handling | StudyRaid

In C, strings are character arrays terminated by a null character \0. Here are the main ways to declare and initialize strings: ... char str1[] = "Hello"; // Array size automatically set char str2[6] = "Hello"; // Explicit size declaration char ...

Filo

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How do you initialize and declare a string in c programming... | Filo

December 12, 2024 - Declare a string using a character array: char str[50]; Initialize a string at the time of declaration: char str[50] = "Hello, World!";

Quora

quora.com › How-do-you-declare-a-string-variable-in-C

How to declare a string variable in C - Quora

Answer (1 of 3): Strictly speaking there is no native string type in C. C developers decided to manage strings as an array of chars ended with a 0. Now, here is the thing, there is a big difference between a string variable and a constant string. That difference is called reserved space. I wil...

Medium

medium.com › @muirujackson › char-pointer-to-string-in-c-aa4b59fdf289

Declaration of String in C. In C, char [] and char * are both used… | by Muiru Jackson | Medium

April 6, 2023 - Attempting to modify a string literal pointed to by a char * results in undefined behavior. Initialization: A char [] can be initialized using a string literal, like "hello", or by assigning each character individually.

reddit.com › r/c_programming › char* vs char[] when initializing a string

r/C_Programming on Reddit: char* vs char[] when initializing a string

August 3, 2022 -

Hello there friends

I am having a problem understanding why this code will work with a string initialized as char[] vs an string initialized as char*. In essence I am trying to reverse a string in place and has written this:

#include <stdio.h>

void revstr(char *str1, int strLen)
{
    // declare variable
    int i, len;
    char temp;

    for (i = 0; i < strLen/2; i++)
    {
        temp = str1[i];
        str1[i] = str1[strLen - i - 1];
        str1[strLen - i - 1] = temp;
    }
}

    int main()
    {

        char str[17] = "This is a string";
        revstr(str,17);
        printf (" After reversing the string: %s", str);

        char* str2 = "Also a string";
        revstr(str2,13);
        printf (" After reversing the string: %s", str2);

    }

When fed the str, the function behaves nicely. When fed the str2, I get a segmentation and I cannot really understand why :/

Anyone care to explain?