Как найти длинну строки

Overview

In C, a string is an array of characters that is terminated with a null character «». The length of a string will be determined by counting all the characters in the string (except for the null character).

Scope of Article

• In this article, we will learn to find the length of a String in C.
• All the methods to find the length of a String will be explained in this article.
• Every method will be explained using syntax, images, and examples.

Introduction

The string length in C is equal to the count of all the characters in it (except the null character «»).

For Example, the string «gfddf» has a length of 5 and the string «4343» has a length of 4.

How to Find the String Length in C?

We can find the length of a String by counting all the characters in it (before the null character) using a for loop. We can also use the built-in string.h library function strlen() or the sizeof() operator.
Let us understand how to use these methods in the coming sections.

String Length in C using a User-Defined Function

We can find the length of a string using a user-defined function by iterating over the string in a for loop and incrementing the count of characters (length) by 1 till it reaches the null character «» and then returning the count.

Let’s take a look at its implementation:
Code

// finding the length of a string using a user-defined function

#include <stdio.h>

// The User-defined method
int str_length(char str[]) {
    // initializing count variable (stores the length of the string)
    int count; 
    
    // incrementing the count till the end of the string
    for (count = 0; str[count] != ''; ++count);
    
    // returning the character count of the string
    return count; 
}

// Driver code
int main() {
    // initializing the array to store string characters
    char str[1000]; 
 
    // inputting the string
    printf("Enter the string: ");
    scanf("%s", str); 
    
    // assigning the count of characters in the string to the length of the string
    int length = str_length(str); 
    
    //  printing the length of string
    printf("The length of the string is %d", length); 
 
    return 0;
}


Output
Enter the string: 567lens
The length of the string is 7


Explanation:
In the above example, we are finding the length of a string by iterating over it in a for loop and incrementing the count by 1 in each iteration till it reaches the null character. The value of count after the end of the for loop will be equal to the length of the string.

String Length in C Using Built-In Library Function

The length of a string can be found using the built-in library function strlen() in string.h header file. It returns the length of the string passed to it (ignoring the null character).

Syntax

The string is passed to the strlen() function, which returns its length.

Let us take a look at its implementation.
Code

// finding the length of a string using the strlen() function from the string.h library

#include <stdio.h>
#include <string.h>

int main() {
    char str[1000]; // initializing the array to store string characters
 
    // inputting the string
    printf("Enter the string: ");
    scanf("%s", str); 
    
    // initializing the length variable
    int length;
    
    // Using the strlen() function to return the length of the string and assign it to the length variable
    length = strlen(str); 
    
    // printing the length of string
    printf("The length of the string is %d", length); 
 
    return 0;
}


Output :
Enter the string: 5654dds
The length of the string is 7


In the above example, we are finding the length of a string by using the string.h library function strlen(), which returns the length of the string passed to it.

String Length in C Using the sizeof() Operator

We can also find the length of a string using the sizeof() Operator in C. The sizeof is a unary operator which returns the size of an entity (variable or value).

Syntax

The value is written with the sizeof operator which returns its size (in bytes).

Let us take a look at its implementation:
Code

// finding the length of a string using the sizeof operator

#include <stdio.h>

int main() {
    // initializing the string literal
    char str[] = "g4343"; 
    
    // printing the string
    printf("The given string is %sn", str);
    
    // initializing the length variable
    int length;
    
    // using the sizeof operator to find the length of the string
    length = sizeof str; 
    
    // printing the length of string
    printf("The length of the string is %d", length-1); 
 
    return 0;
}


Output
The given string is g4343
The length of the string is 5


In the above example, we are finding the length of the string «g4343» using the sizeof operator in C. The sizeof operator returns its length as 6 in the output as It returns the size of an operand, not the string length (including null values). But here, if we print length-1 then we get the length of the string.

Conclusion

• In C, the length of a string is the count of all its characters except the null character «».
• We can find the length of the string using a for loop by counting each character in each iteration.
• The built-in library function strlen() is used to return the length of a string passed to it.
• We can also find the length of a C String using the sizeof operator.