How can take a string from command line with main function has no parameter and convert the string in uppercase?

void main()

{

char str[15];

int i=0;

strcpy(str,_argv[1]);

for(i=0;i<=strlen(str);i++)

{

if(str[i]>=97&&str[i]<=122)

str[i]=str[i]-32;

}

printf("\nstring in uppercase : %s",str);

}