Sizeof output is not as expected-CodePudding

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

int main() {
   char str[400] = "rQvqQmyl9N9FmI8ECESs0N2dKBATuIrvT4HEh0lRa 6kGHIP0owiFqFdlvktmOQMTdZ5gW44G2O6T2uQGlIeeobnyYuZscLadvyM5tkzb1MhEmBoIuCp8db9GZ8SBBMnoDIWNi9Ad6pRzBpcxmobWJnJo3O6BQ/Kii03RMfXVEw5No7n576J0blLPirrH6M7OaIp7qcrT7hD4qHkGIKjoAcGLsu0c5Ii2r lOnFE1zgMPZtw8 QoHBp/lzFH5LyB973e k9B5T3UO/L7xM6h8ZN4ufXibM385PdzPuwZ3NbmZRCSpIrvGNyUSZo0/mcPuzt6KuoQpNLYt9Avmi";
   // Extract the first token
   char * token = strtok(str, " ");
   printf( " %s\n", token ); //printing the token
   printf("%lu \n", sizeof(token));
   return 0;
}

Output rQvqQmyl9N9FmI8ECESs0N2dKBATuIrvT4HEh0lRa 6kGHIP0owiFqFdlvktmOQMTdZ5gW44G2O6T2uQGlIeeobnyYuZscLadvyM5tkzb1MhEmBoIuCp8db9GZ8SBBMnoDIWNi9Ad6pRzBpcxmobWJnJo3O6BQ/Kii03RMfXVEw5No7n576J0blLPirrH6M7OaIp7qcrT7hD4qHkGIKjoAcGLsu0c5Ii2r lOnFE1zgMPZtw8 QoHBp/lzFH5LyB973e k9B5T3UO/L7xM6h8ZN4ufXibM385PdzPuwZ3NbmZRCSpIrvGNyUSZo0/mcPuzt6KuoQpNLYt9Avmi

Why Size of token is 8 ? It should be length of token.

CodePudding user response：

The variable token has the type char * that is it is a pointer

char * token = strtok(str, " ");

So this call of printf

printf("%lu \n", sizeof(token));

outputs the size of a pointer in your system.

You will get the same result if you will use even an uninitialized pointer that does not point to any string as for example

char *token;
printf( "%zu \n", sizeof(token));

If you want to output the length of the pointed string then you need to write

printf("%zu \n", strlen(token));

CodePudding user response：

sizeof is for managing memory, not data. It tells you how much memory a type requires. sizeof an array is the number of bytes the array requires. sizeof a pointer is the number of bytes the pointer requires.

strlen is for managing the data of strings. It tells you how long a string is, which is the number of non-zero characters before the first zero character.

CodePudding user response：

The eight is the size of your pointer which is platform dependent. What you need is to iterate through the token variable or use strlen(token) to get the actual size.