pointer to an array of pointers

[ramu]

Hi,
Could anyone please tell me how to dereference a pointer to an
array of pointers?

Regards

[vippstar]

On Dec 3, 7:13 pm, ramu <ramu....@gmail .comwrote:

Hi,
Could anyone please tell me how to dereference a pointer to an
array of pointers?

Regards

*p or p[0].

A pointer to an array of N pointers is char *(*)[N].

Example:

char *(*foo)[N] = NULL;

[Malcolm McLean]

"ramu" <ra******@gmail .comwrote in message
news:f0******** *************** ***********@s8g 2000prg.googleg roups.com...

Hi,
Could anyone please tell me how to dereference a pointer to an
array of pointers?

/* set up a pointer to a list of pointers, here strings for readability */
char **strings;
int i;

strings = malloc(12 * sizeof(char *));
for(i=0;i<12;i+ +)
{
strings[i] = malloc(32);
sprintf(strings[i], "string %d", i+1);
}

/* dereference to get a string, or char * */
printf("%s\n", strings[3]);
/* dereference to get a character, should be the letter g */
printf("%c\n", strings[3][5]);

As you can see, when you say "dereferenc e the pointer" you can mean either
get what it points to immediately, which is another pointer, or what it
points to ultimately, which in this case is a char.

Also we can use this syntax

/* treat as pointer to single element */
printf("%s\n", *strings);

/* get first element of first element */
printf("%c\n", **strings);

This isn't so useful as the first. Usually when you want a pointer it is
because you have an array of things to point to, pointers to single items
are less common. However you'll need to know both syntaxes.

--
Free games and programming goodies.
http://www.personal.leeds.ac.uk/~bgy1mm

[vippstar]

On Dec 3, 11:20 pm, "Malcolm McLean" <regniz...@btin ternet.comwrote :

"ramu" <ramu....@gmail .comwrote in message

news:f0******** *************** ***********@s8g 2000prg.googleg roups.com...Hi,

Could anyone please tell me how to dereference a pointer to an
array of pointers?

/* set up a pointer to a list of pointers, here strings for readability */
char **strings;
int i;

strings = malloc(12 * sizeof(char *));
for(i=0;i<12;i+ +)
{
strings[i] = malloc(32);
sprintf(strings[i], "string %d", i+1);

}

/* dereference to get a string, or char * */
printf("%s\n", strings[3]);
/* dereference to get a character, should be the letter g */
printf("%c\n", strings[3][5]);

As you can see, when you say "dereferenc e the pointer" you can mean either
get what it points to immediately, which is another pointer, or what it
points to ultimately, which in this case is a char.

When you dereference a pointer you mean access what it points to.
In strings[3][5] you're dereferencing two pointers. strings and
strings[3].

Also we can use this syntax

/* treat as pointer to single element */
printf("%s\n", *strings);

*strings is equal to strings[0] and it has nothing to do with 'single
element'.
A pointer is of scalar type.

Really, i don't undestand your post, OP asked for a pointer to array
of pointers and you answered with a char **?

[CBFalconer]

vi******@gmail. com wrote:

>

.... snip ...

>
Really, i don't undestand your post, OP asked for a pointer to
array of pointers and you answered with a char **?

A char** is a pointer to a pointer to char, which is what a
function will receive as a parameter to describe an array of
pointers to char. Remember that under most conditions an array is
described by a pointer to its zeroth element.

--
Chuck F (cbfalconer at maineline dot net)
<http://cbfalconer.home .att.net>
Try the download section.

--
Posted via a free Usenet account from http://www.teranews.com

[Barry Schwarz]

On Mon, 3 Dec 2007 09:13:14 -0800 (PST), ramu <ra******@gmail .com>
wrote:

>Hi,
Could anyone please tell me how to dereference a pointer to an
array of pointers?

In strict terminology, a pointer to an array of pointers is
TYPE *arr[N];
TYPE *(*ptr)[N];
ptr = &arr;
ptr is a pointer to an array of N pointer to TYPE and points to one
such array.

In this case, ptr[0] is the array itself and ptr[0][i] is the i-th
pointer in the array.

Frequent, as in 99+%, newcomers to the language use the term to mean
TYPE *arr[N]
TYPE **ptr;
ptr =arr; /* or the equivalent ptr = &arr[0]; */
ptr is a pointer to pointer to TYPE and points to the first pointer in
the array of such pointers.

In this case, the slightly simpler ptr[i] is the i-th pointer in the
array.

Which one did you mean?
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