strlen() function in c

The strlen() function returns the number of characters in a string. It is declared in the <string.h> header file and does not count the null terminator '\0'.

strlen() counts all characters in the string until it encounters the null character '\0'.
It returns the length of the string as a value of type size_t.

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

int main() {
    char str[] = "GeeksforGeeks";

    printf("Length of the string: %zu\n", strlen(str));

    return 0;
}

Output

Length of the string: 13

Syntax

The syntax of strlen() function in C is as follows:

size_t strlen(const char* str);

Parameters

The strlen() function only takes a single parameter.

str: It represents the string variable whose length we have to find.

Return Value

This function returns the integral length of the string passed.

Important Points about strlen()

The following points should be kept in mind while using strlen():

strlen() does not count the NULL character '\0'.
The time complexity of strlen() is O(n), where n is the number of characters in the string.
Its return type is size_t ( which is generally unsigned int ).

Applications of strlen() in C

The strlen() function is widely used in C programs to determine the length of a string before performing various string operations.

Finding the number of characters in a string.
Validating the length of user input.
Comparing string lengths before processing.
Controlling loops that iterate through string characters.
Performing string manipulation tasks such as concatenation, copying, and formatting.
Checking whether a string is empty (strlen(str) == 0).

Syntax

Important Points about strlen()

Applications of strlen() in C

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