memset

Function Usage

Populates a value into each byte of a memory block. It is usually used to initialize or clear the memory block.

Function Syntax

void *memset(void *ptr, int value, size_t num);

Parameters

Parameter	Description	Value Range	Input/Output
ptr	Pointer to the destination memory used to store the reset data.	Non-null pointer to a valid memory block, with at least num bytes accessible.	Input/Output
value	Target value, which will be converted into the unsigned char type.	0 to 255. The excess part will be truncated.	Input
num	Number of bytes to be reset.	Non-negative number that does not exceed the size of the memory block pointed to by ptr.	Input

Return Value

Success: A pointer to the destination memory is returned. The return value is generally ignored.
Failure: See those of open source glibc. No other exception values will be returned.

This function is used to initialize or clear a memory block by filling it with 0 or another value on a byte-by-byte basis. Therefore, the size of the value should be taken into account.

Example

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

int main() {
    char byteArr[10];
    memset(byteArr, 'A', sizeof(byteArr));
    for(int i = 0; i < sizeof(byteArr); i++) {
        printf("%c ", byteArr[i]);
    }
    printf("\n");
    return 0;
}

Output:

A A A A A A A A A A

Parent topic: Function Syntax