C Program to find the length of a string without using strlen()

In this C Programming example, we will implement the program to find the length of a string without using strlen() and print the output on the console.

1. Length of String

The length of a string can be calculated by iterating over the characters one by one until the loop reaches the end of the string and encounters a null value “\0“.

Example
Input: Hello World
Output: Length of the string: 11

Helpful topics to understand this program better are-

• Data Types in C
• Console Input / Output in C
• Functions in C
• For and While Loop in C

2. C Program to find the length of a string without using strlen()

Let’s discuss the execution(kind of pseudocode) for the programto find length of a string without using strlen() in C.

1. Initially, the program will prompt the user to enter the string.
2. Here fgets(input, 100, stdin) reads the string entered by the user and passes the string in the for loop.
3. Now, in for(i=0; input[i] != '\0' && input[i] != '\n'; i++) loop, the program iterates over the characters in the string until it reaches the null value '\0' or a new line '\n' and increments the value of i by 1.
4. When the loop ends the length of the string will be printed on the console.

Let us now implement the above execution of the program to find the length of a string without using strlen() in C.

#include <stdio.h>
int main() {
  char input[100];
  int i, length = 0;

  printf("Enter a string \n");
  fgets(input, 100, stdin);

  for (i = 0; input[i] != '\0' && input[i] != '\n'; i++) {
    length++;
  }
  printf("Length of the string: %d", length);

  return 0;
}

Note: In the above program we can also use a while loop and the string entered must be under the range of char[] as declared in the program.

Output
Enter a string
Codingeek.com
Length of the string: 13

3. Conclusion

In this C Programming example, we have discussed how to find the length of a string without using strlen() in C.

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