Well! We have situations where we need several pointers, say several strings to be matched for desired one, for example, then declaring and initializing pointers one by one as scalar is a cumbersome job. We have a way out to this trouble and which is declare and initialize an array of pointers. Let’s go for it.
char *car_make[9] = {"Suzuki","Toyota","Nissan","Tata","BMW","Audi", "Chevrolet","Honda","Mahindra"};
Let’s presume the declaration “char *car_make[9]” as an expression and evaluate it to understand about how to declare and initialize correctly an array of pointers.
In the expression
char *car_make[9]
subscript operator ‘[]’ being higher in precedence than indirection operator ‘*’ and therefore is evaluated first, results in 9 characters. Then, indirection is applied which results in 9 ‘pointers-to-char’ or 9 ‘pointers-to-strings’. Let’s rewrite the above expression
char *car_make[9]
as
char (*car_make)[9]
and this time, again, try to evaluate the expression.
This time, indirection operator ‘*’, enclosed in parenthesis, go first than subscript operator. This results in ‘pointer-to-something’. Then subscript operator evaluates to an ‘array of 9 characters’. And overall result is a ‘pointer-to-array_of_9_characters’, which is not what we are interested in. In fact, we require an array of pointers. Therefore, expression
char *car_make[9]
is what serves our purpose. Let’s see how this initialization takes place,
char *car_make[9] = {"Suzuki","Toyota","Nissan","Tata","BMW","Audi", "Chevrolet","Honda","Mahindra"};
*car_make[0] = "Suzuki"; /* '*car_make[]' is a ptr-to-string */ *car_make[1] = "Toyota"; *car_make[2] = "Nissan"; *car_make[3] = "Tata"; *car_make[4] = "BMW"; *car_make[5] = "Audi"; *car_make[6] = "Chevrolet"; *car_make[7] = "Honda"; *car_make[8] = "Mahindra";
Let’s consider a program using the above array of ‘pointer-to-strigs’ to ensure if a given string is in the array or not.
/* * arr_ptr2char.c -- program shows if a given string is matched in the list * of strings */ #include <stdio.h> #include <string.h> /* function prototype */ void match_str(char const * const, char const * const[], int const); int main(void) { char const *car_make[9] = {"Suzuki","Toyota","Nissan","Tata","BMW", "Audi","Chevrolet","Honda","Mahindra"}; char to_search[15]; printf("Give choice of \'car make\' u want to search for...\n"); gets(to_search); match_str(to_search, car_make, 9); return 0; } void match_str(char const * const to_match, char const * const arr_str[], int const size) { char const **check_make; for (check_make = arr_str; check_make < arr_str + size; check_make++) if (strcmp(to_match, *check_make) == 0) { printf("Matched at location %d in car_make.\n", check_make - arr_str); return; } printf("Not matched!\n"); return; }
Let’s now try out above program for some test-choices,
Give choice of 'car make' u want to search for... Nissan Matched at location 2 in car_make. Give choice of 'car make' u want to search for... Tata Matched at location 3 in car_make. Give choice of 'car make' u want to search for... Ambassador Not matched!
Sanfoundry Global Education & Learning Series – 1000 C Tutorials.
