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What is the difference between these two pointer declarations?

Are these declarations different or do the produce the same result?

char * const *argv;

and

const char **argv;

Is there a difference or are both pointer to a pointer?

The background is that I was writing a C commandline shell and used this struct for a command:

struct command
{
    char * const *argv;
};

The above struct was used to call exec. Now when I looked at another question then the struct was different:

Connecting n commands with pipes in a shell?

In that question the struct to achieve the same is different.

Solution

  • They are totally different:

    char *const *argv; declares "a pointer to const pointer to char";

    const char **argv; declares "a pointer to pointer to const char";

    Also, char **const argv; declares "a const pointer to pointer to char".

    To understand these declarations, try reading them "inside out": http://c-faq.com/decl/cdecl1.html