JIYIK CN >

This article will introduce several methods to clear character arrays in C language.

memsetUse function to clear char array in C language

memsetThe _set_storage_region function is commonly used to set a storage area to a constant value. This function is part of the standard library and <string.h>is defined in the _set_storage_region header file.

memsetIt takes three parameters - the first one is voidthe pointer to the memory area, the second one is the constant byte value and the last one represents the number of bytes to be filled at the given memory address. Note that we can 0clear the character array by an integer value.

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

void printCharArray(char *arr, size_t len)
{
    printf("arr: ");
    for (size_t i = 0; i < len; ++i) {
        printf("%c, ", arr[i]);
    }
    printf("\n");
}

#define LENGTH 20

int main(){
    char c_arr[LENGTH] = {'a', 'b', 'c', 'd', 'e', 'f', 'g'};
    printCharArray(c_arr, LENGTH);

    memset(c_arr, 0, LENGTH);
    printCharArray(c_arr, LENGTH);

    exit(EXIT_SUCCESS);
}

Output:

arr: a, b, c, d, e, f, g,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,
arr:  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,

Alternatively, memsetit can be called with a specific character as the constant byte parameter, which is useful for initializing each given array element with the same value. In this case, we arbitrarily choose the character 0to fill the array, resulting in an empty memory area.

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

void printCharArray(char *arr, size_t len)
{
    printf("arr: ");
    for (size_t i = 0; i < len; ++i) {
        printf("%c, ", arr[i]);
    }
    printf("\n");
}

#define LENGTH 20

int main(){
    char c_arr2[LENGTH] = "techarmp array";
    printCharArray(c_arr2, LENGTH);
    memset(c_arr2, '0', LENGTH);
    printCharArray(c_arr2, LENGTH);

    exit(EXIT_SUCCESS);
}

Output:

arr: t, e, m, p,  , a, r, r, a, y,  ,  ,  ,  ,  ,  ,  ,  ,  ,  ,
arr: 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

Clearing a character array in C using the bzeroor functionexplicit_bzero

bzerois another standard library function that 0fills a memory area with bytes. It requires only two parameters - a pointer to the memory area and the number of bytes to be overwritten. on the other hand, explicit_bzerois an alternative that guarantees a write operation regardless of compiler optimizations. The compiler analyzes the code for redundant instructions and removes them if the user instructs it to do so, and explicit_bzerothe function is designed for this special case.

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

void printCharArray(char *arr, size_t len)
{
    printf("arr: ");
    for (size_t i = 0; i < len; ++i) {
        printf("%c, ", arr[i]);
    }
    printf("\n");
}

#define LENGTH 20

int main(){
    char c_arr[LENGTH] = {'a', 'b', 'c', 'd', 'e', 'f', 'g'};
    printCharArray(c_arr, LENGTH);

    bzero(c_arr, LENGTH);
    printCharArray(c_arr, LENGTH);

    explicit_bzero(c_arr, LENGTH);
    printCharArray(c_arr, LENGTH);

    exit(EXIT_SUCCESS);
}