How to rotate strings

char buf[BUFSIZE];
strncpy(buf, "...", BUFSIZE-1);
buf[BUFSIZE-1] = '\0';
size_t len = length(buf);
size_t i = 0;
while(i < len && !is_vowel(buf[i])) i++;
if (i < len) rotate(buf, i);

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

int main(){
	char str[100],rtStr[100];
	int len,i,flag=0,vowel_pos,c=0;
	
	printf("Enter the string: ");
	scanf("%s",&str);
	
	for(i=0;i<strlen(str);i++){>
		if(str[i]=='a' || str[i]=='e' || str[i]=='i' || str[i]=='o' || str[i]=='u' || str[i]=='A' || str[i]=='E' || str[i]=='I' || str[i]=='O' || str[i]=='U'){
			vowel_pos=i;
			flag=1;
			break;
		}
	}
	
	//Vawel is found and string will be arrange
	if(flag==1){
		 while (c < (strlen(str)-vowel_pos)) {
	    	rtStr[c] = str[vowel_pos+c];
	      	c++;
	    }
		
	    for(i=0;i<vowel_pos;i++){>
	    	rtStr[c]=str[i];	    	
	    	c++;
	    }
	    rtStr[c] = '\0';
	    printf("Rotate String is: %s",rtStr);
	}
	//Vawel is not found, so the string will be unchanged
	else{
		printf("Rotate String is: %s",str);
	}
	
	return 0;
}