Header File 

mem.h, string.h  

Category 

Memory and String Manipulation Routines, Inline Routines, C++ Prototyped Routines 

Prototype 

void *memchr(const void s, int c, size_t n);/ C only */ 

const void *memchr(const void *s, int c, size_t n);// C++ only 

void *memchr(void *s, int c, size_t n);// C++ only 

void *memchr(const void s, int c, size_t n);/ C and C++ */ 

void * _wmemchr(void s, int c, size_t n);/ unicode version */ 

Description 

Searches n bytes for character c. 

memchr is available on UNIX System V systems. 

memchr searches the first n bytes of the block pointed to by s for character c. 

Return Value 

On success, memchr returns a pointer to the first occurrence of c in s; otherwise, it returns NULL.

#include <string.h>
#include <stdio.h>
int main(void)
{
    char str[17];
    char *ptr;
    strcpy(str, "This is a string");
    ptr = (char *) memchr(str, 'r', strlen(str));
    if (ptr)
       printf("The character 'r' is at position: %d\n", ptr - str);
    else
       printf("The character was not found\n");
    return 0;
}

Portability