I am not very experienced in C. I am trying to have some code that works like this:
Declare array of strings;
Function that erases array of strings and inserts a new set of strings (number unknown)
How can I do this? I know I can do const char *a[2]; but that requires entering an array size when I declare it. Can I make a variable for my string array that can support multiple sizes?
You can use pointers to pointers.
char **strings;
Here is how you would create it: (where <size> is the size of the array)
strings = malloc(sizeof(char*) * <size>);
Now setting/getting elements is pretty simple:
strings[0] = "hello";
printf("%s", strings[0]);
Just a warning, the memory is not already set to fully null strings. If you want all of the strings to be empty by default then use calloc() instead of malloc():
strings = calloc(sizeof(char*) , <size>);
You can control array size like this:
int size;
char *a[size];
printf("enter size");
scanf("%d",&size);
You have to use a char**, a pointer to pointer to char, to by able to capture a dynamic array of strings.
If you want 10 strings, you have to use:
char** strings = (char**)malloc(sizeof(char*)*10);
To store a string in the first element of the array, you have to use:
strings[0] = malloc(strlen("abcd")+1);
strpcy(strings[0], "abcd");
Here's a program that demonstrates the whole thing:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main()
{
char string[200];
char** strings = NULL;
int numStrings = 0;
int n = 0;
int i = 0;
/* Read the number of strings */
do
{
printf("Enter the number of strings (0 or higher): ");
n = scanf("%d", &numStrings);
} while ( n != 1 || numStrings < 0 );
/* Eat up the remaining characters afte the integer */
fgets(string, 199, stdin);
if ( numStrings > 0 )
{
/* Read the strings */
strings = (char**)malloc(numStrings*sizeof(char*));
for ( i = 0; i != numStrings; ++i )
{
printf("Enter a string: ");
fgets(string, 199, stdin);
strings[i] = malloc(strlen(string)+1);
strcpy(strings[i], string);
}
/* Print the strings back */
for ( i = 0; i != numStrings; ++i )
{
printf("%s", strings[i]);
}
/* Now release the memory back to the system */
/* First the individual strings */
for ( i = 0; i != numStrings; ++i )
{
free(strings[i]);
}
/* Now the array */
free(strings);
}
return 0;
}
strings[0] = "abcd"; It's both faster and shorter