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#include <ctype.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <stdlib.h>
int main(void)
{
char* astring = strdup("this is a string # with something to seek");
size_t len = strlen(astring);
memccpy(astring+10, astring, '#', len-10);
sprintf(astring, "this is a string # with something to seek");
memccpy(astring, astring+10, '#', len);
sprintf(astring, "this is a string # with something to seek");
/*
* space is earlier than len, no overlap
* "this " gets copied (up to and including the first ' ')
* and it overwrites the destination starting with the 's' of "string"
* so res will point to the 'g' of "string"
*/
char* res = memccpy(astring+10, astring, ' ', len-10);
assert(res && *res == 'g');
sprintf(astring, "this is a string # with something to seek");
/* length is 0, nothing copied, returns NULL */
res = memccpy(astring, "abcdefhhijklmnopqrstuvwxy", 'z', 0);
assert(NULL == res);
/* 'z' not found so 20 bytes copied, returns NULL */
res = memccpy(astring, "abcdefhhijklmnopqrstuvwxy", 'z', 20);
assert(NULL == res);
free(astring);
}
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