memchr function

C

Function

Reference manual

@see man memchr

The memchr function searches for a specific byte in a block of memory. It scans the first n bytes of the memory area pointed to by ptr for the first occurrence of the byte c.

Syntax

void *memchr(const void *ptr, int c, size_t n);

Parameters

• ptr: A pointer to the memory area to be searched.
• c: The byte to be located.
• n: The number of bytes to be examined.

Return value

• If the byte c is found, a pointer to the first occurrence is returned.
• If c is not found within the first n bytes, the function returns NULL.

Example

In the following example we use the memchr function to search for a byte containing the value ‘W’ in the string “Hello World!”, if the byte is located we print the position at which it was located else we print an error message.

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

int main(void) {
    const char str[] = "Hello, World!";
    const char *ptr = memchr(str, 'W', strlen(str));
    
    if (ptr != NULL)
        printf("Found 'W' at position %ld\n", ptr - str);
    else
        printf("Character not found.\n");
    return (0);
}