fgets reads 4 charachters when buffer is 5

When using the input hello world to this program it outputs hell which is less than 5 why does this happen

void grab_user_input()
{
    char user_input[10];
    if ( fgets(user_input, 5 , stdin ) !=  NULL )
    {
        printf("%s\n",user_input);
    }
}

int main()
{

    grab_user_input();
    return 0;
}

>Solution :

The last byte is the null byte \0.

Read the fgets manual for more info. Here’s an excerpt:

char *fgets( char *restrict str, int count, FILE *restrict stream );

Reads at most count - 1 characters from the given file stream and stores them in the character array pointed to by str. Parsing stops if a newline character is found, in which case str will contain that newline character, or if end-of-file occurs. If bytes are read and no errors occur, writes a null character at the position immediately after the last character written to str.