strset() and a Portable Character-Replacement Function

strset() is a non-standard extension that replaces every character of a string with one chosen character while preserving the terminating null character. The same behavior is easy to implement portably.

Legacy Syntax Top ↑

strset(string, '*');  // non-standard

Portable Replacement Top ↑

#include <stdio.h>

void set_all_chars(char text[], char replacement) {
    for (size_t i = 0; text[i] != '\0'; i++) {
        text[i] = replacement;
    }
}

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

    set_all_chars(text, '*');
    printf("%s\n", text);

    return 0;
}

Output

********

Empty String Behavior Top ↑

#include <stdio.h>

void set_all_chars(char text[], char replacement) {
    for (size_t i = 0; text[i] != '\0'; i++) {
        text[i] = replacement;
    }
}

int main(void) {
    char empty[] = "";

    set_all_chars(empty, '#');
    printf("Length remains zero: \"%s\"\n", empty);

    return 0;
}

Preserved Edge-Case Variations Top ↑

Null-Safe Portable Replacement

#include <stdio.h>

int set_all_chars(char *text, char replacement) {
    if (text == NULL) {
        return 0;
    }

    while (*text != '\0') {
        *text = replacement;
        text++;
    }

    return 1;
}

int main(void) {
    char *text = NULL;

    if (!set_all_chars(text, '*')) {
        printf("String is NULL.\n");
    }

    return 0;
}

Replace Every Character in a String Containing Punctuation and Digits

#include <stdio.h>

void set_all_chars(char text[], char replacement) {
    for (size_t i = 0; text[i] != '\0'; i++) {
        text[i] = replacement;
    }
}

int main(void) {
    char text[] = "Hello, World! 123";

    set_all_chars(text, '#');
    printf("%s\n", text);

    return 0;
}

Output

#################

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.

About the author   Watch on YouTube

Connect: