When Do Triple Pointers Become Necessary?

Multiple Levels of Pointer Dereferences: Beyond Double Pointers

In programming, pointers provide a way to indirectly access the memory address of a variable. However, in some instances, a single pointer is insufficient, requiring the use of multiple levels of pointer dereferences.

When Triple Pointers Make Sense

Consider the following code:

char ***ptr;

Imagine you are writing a tool similar to the bash shell, which manages processes in a hierarchical manner. To represent the complex environment of each process, you may define a structure named invocation that includes a pointer to an array of environment variables:

struct invocation {
    ...
    char** env;
    ...
};

To browse the environment variables of multiple processes, you could create an array of invocation instances and pass it to a function, as follows:

void browse_env(size_t envc, char*** env_list);

In this context, char*** env_list is a pointer to an array of pointers to arrays of pointers to char. This structure allows you to traverse the hierarchy:

• env_list: Pointer to an array of pointers to arrays of characters
• env_list[i]: Pointer to an array of pointers to characters (each representing an environment variable)
• env_list[i][j]: Pointer to a character (an individual environment variable)

This complex pointer structure enables the traversal of a hierarchical data structure (a list of invocation instances with their environment variables) and allows for efficient manipulation of the environment settings for each process.

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