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Showing content from https://cplusplus.com/reference/cstring/memchr/ below:

function

memchr

const void * memchr ( const void * ptr, int value, size_t num );      void * memchr (       void * ptr, int value, size_t num );

Locate character in block of memory

Searches within the first num bytes of the block of memory pointed by ptr for the first occurrence of value (interpreted as an unsigned char), and returns a pointer to it.

Both value and each of the bytes checked on the the ptr array are interpreted as unsigned char for the comparison.

Parameters

ptr: Pointer to the block of memory where the search is performed.
value: Value to be located. The value is passed as an int, but the function performs a byte per byte search using the unsigned char conversion of this value.
num: Number of bytes to be analyzed.
size_t is an unsigned integral type.

Return Value A pointer to the first occurrence of value in the block of memory pointed by ptr.
If the value is not found, the function returns a null pointer.

Portability In C, this function is only declared as:

void * memchr ( const void *, int, size_t );

instead of the two overloaded versions provided in C++.

Example

/* memchr example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char * pch;
  char str[] = "Example string";
  pch = (char*) memchr (str, 'p', strlen(str));
  if (pch!=NULL)
    printf ("'p' found at position %d.\n", pch-str+1);
  else
    printf ("'p' not found.\n");
  return 0;
}

Output:

See also

memcmp: Compare two blocks of memory (function)

strchr: Locate first occurrence of character in string (function)

strrchr: Locate last occurrence of character in string (function)

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