std::memchr

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Technical specifications

Symbols index

External libraries

 

Strings library

Null-terminated strings

Byte strings

Multibyte strings

Wide strings

Classes

basic_string

basic_string_view (C++17)

char_traits

 

Null-terminated byte strings

Functions
Character manipulation
isalnum isalpha islower isupper isdigit isxdigit isblank (C++11)	iscntrl isgraph isspace isprint ispunct tolower toupper
Conversions to numeric formats
atof atoiatolatoll (C++11) strtolstrtoll (C++11)	strtoulstrtoull (C++11) strtofstrtodstrtold (C++11)(C++11) strtoimaxstrtouimax (C++11)(C++11)
String manipulation
strcpy strncpy strxfrm	strcat strncat
String examination
strlen strcmp strncmp strcoll strchr strrchr	strspn strcspn strpbrk strstr strtok
Memory manipulation
memchr memcmp memset	memcpy memmove
Miscellaneous
strerror

 

Defined in header <cstring>
const void* memchr( const void* ptr, int ch, std::size_t count );
void* memchr(       void* ptr, int ch, std::size_t count );

Converts ch to unsigned char and locates the first occurrence of that value in the initial count bytes (each interpreted as unsigned char) of the object pointed to by ptr.

This function behaves as if it reads the bytes sequentially and stops as soon as a matching bytes is found: if the array pointed to by ptr is smaller than count, but the match is found within the array, the behavior is well-defined.

(since C++17)

Parameters

ptr	-	pointer to the object to be examined
ch	-	byte to search for
count	-	max number of bytes to examine

Return value

Pointer to the location of the byte, or a null pointer if no such byte is found.

Example

Search an array of characters.

Run this code

#include <cstring>
#include <iostream>
 
int main()
{
    char arr[] = {'a', '\0', 'a', 'A', 'a', 'a', 'A', 'a'};
    char *pc = (char*) std::memchr(arr, 'A', sizeof arr);
    if (pc != nullptr)
        std::cout << "search character found\n";
    else
        std::cout << "search character not found\n";
}

Output:

search character found

See also

strchr	finds the first occurrence of a character (function)
findfind_iffind_if_not (C++11)	finds the first element satisfying specific criteria (function template)