Derek Martin wrote:
On Mon, Oct 31, 2005 at 01:30:44PM -0600, STYMA, ROBERT E (ROBERT) wrote:
The syntax: int main(int argc, char **argv) works, but most of the C books I have seen recommend the *argv[] version.
I meant to comment that these two different notations are functionally identical; an array name is nothing more than a pointer. For example, if we have the following code:
Not true. Or rather, only partially true. In a variable declaration the two are *not* equivalent. In a parameter declaration and in an expression, the two *are* equivalent. The difference is, in a variable declaration, you also specify how much space is to be allocated for the variable, which is not the case for the other uses. So, the books are indeed correct, **argv and *argv[] are equivalent *when used in the parameter list*.
#include <stdio.h> void main (void){
char foo[] = "This is a string\n";
And this is totally different from char *foo = "This is a string\n"; The former declares an array and gives it a name, the latter declares an anonymous array (string) and creates a pointer to it. With the former declaration, you cannot alter the value of foo, with the latter you can (alter as in foo = some_other_value; or foo++;).
char *bar = foo; /* these expressions all print "T\n" */ printf("%c\n", foo[0]); printf("%c\n", *bar); printf("%c\n", bar[0]); printf("%c\n", *foo); /* these expressions all print "i\n" */ printf("%c\n", foo[2]); printf("%c\n", *(bar + 2)); printf("%c\n", bar[2]); printf("%c\n", *(foo + 2));}
The results may surprise programming students:
$ gcc -o ptr ptr.c ptr.c: In function `main': ptr.c:2: warning: return type of 'main' is not `int' [ddm@archonis ~] $ ./ptr T T T T i i i i
In reality, foo[x] is just "syntactic sugar" for *(foo + x). This is called pointer math, and works properly regardless of the size and type of foo, so long as it was declared properly before being used.
[I'm very bored today...]