strlen() in C: Length of a String

strlen() returns the number of characters in a null-terminated string, excluding the terminating \0. It is declared in <string.h> and returns size_t.

Syntax Top ↑

size_t length = strlen(string);

Basic strlen() Example Top ↑

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

int main(void) {
    char text[] = "plus2net";
    size_t length = strlen(text);

    printf("Length: %zu\n", length);
    return 0;
}

Output

Length: 8

Count Characters Without strlen() Top ↑

#include <stdio.h>

int main(void) {
    char text[] = "plus2net";
    size_t length = 0;

    while (text[length] != '\0') {
        printf("Index %zu: %c\n", length, text[length]);
        length++;
    }

    printf("Length: %zu\n", length);
    return 0;
}

Length of User Input Top ↑

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

int main(void) {
    char text[100];

    printf("Enter a string: ");
    if (fgets(text, sizeof(text), stdin) == NULL) {
        return 1;
    }

    text[strcspn(text, "\n")] = '\0';
    printf("Length: %zu\n", strlen(text));
    return 0;
}

Spaces Count as Characters Top ↑

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

int main(void) {
    char text[] = "C programming";
    size_t length = strlen(text);

    for (size_t i = 0; i < length; i++) {
        printf("Position %zu: %c\n", i, text[i]);
    }

    printf("Length: %zu\n", length);
    return 0;
}

The space between C and programming contributes one character to the total length.

Preserved Example: Use strlen() in a Loop Top ↑

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

int main(void) {
    char text[] = "C programming";
    size_t length = strlen(text);

    for (size_t i = 0; i < length; i++) {
        printf("Character at position %zu: %c\n", i, text[i]);
    }

    return 0;
}

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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