Programming Forums > Application Development > C++

Symptom · Jan 29th, 2006, 10:52 AM

You should use malloc to reserve space for the char array as DaWei said. Do something like

char message[1024];
char* begin;
begin = (char*) malloc (sizeof(char) * (strlen(message)+1));
strncpy(begin,message,(strlen(message)+1));

The above code copies the string inside the begin char array.
You could use 2 arrays, one to store the command and one to store the argument. It's all up to you...

nnxion · Jan 29th, 2006, 11:11 AM

I don't see why you don't use the keyword new. Or why you're not using C++ strings.

Cache · Jan 29th, 2006, 11:17 AM

You don't need either malloc or new:

(Toggle Plain Text)

#include <iostream>

using namespace std;

int main ()
{
	char message[1024];
   char* begin;

   cin.getline(message, 1024);

   begin = message + 4;
   
   cout << begin;
	
	cin.sync();
	cin.get();
	return 0;
}

EDIT: Just be aware that 'begin' is pointing to the actual location of message[3]. So any changes made to 'message + 4' or above will be seen from 'begin' also.

Cache · Jan 29th, 2006, 12:17 PM

I really wish the edit time on this forum would be extended slightly. Anyway, I just wanted to say: on reflection, it does actually look a lot cleaner to use new, and negates the need for a second variable:

(Toggle Plain Text)

#include <iostream>

using namespace std;

int main ()
{
	char *message = new char[1024];
   
   cin.getline(message, 1024);
   message += 4;
   
   cout << message;
	
   cin.sync();
   cin.get();
   delete [] message;
   return 0;
}

Infinite Recursion · Jan 30th, 2006, 8:50 AM

Just a possible alternative... how about using strings?

string s = "say hello";
s = s.substr(5,s.length());

DaWei · Jan 30th, 2006, 8:56 AM

Suggested in posts #7 and #12, IR, and apparently rejected

.

Infinite Recursion · Jan 30th, 2006, 9:26 AM

Missed it... I guess I read too many threads this morning... lines are running together.
I should probably go get my morning supply of caffeine.

Cache · Jan 30th, 2006, 3:27 PM

Quote:

Originally Posted by jayme

This also has to be done in a char, not a string. Thx

That's why I persisted with C-style strings during this thread. Also note: the string will always start of as a C-style string - since the string is to be filled from a recv operation (I have no doubt both of you already know this). Although 1024 bytes being copied to a std::string after the initial recv isn't such a penalty, I guess.

Polyphemus_ · Jan 30th, 2006, 3:32 PM

If you want the first 4 characters deleted, you could also do this:

(Toggle Plain Text)

strcmp(message, message + 4);

I'm not sure this will work on every C library, since implementations can always do things weird

.

DaWei · Jan 30th, 2006, 3:52 PM

strcmp is a string comparison function. Perhaps you were thinking of strcpy. Both are standard library functions. If an implementation doesn't handle them, the implementation is broken.

As far as there being a time penalty for C++ strings versus char arrays, no biggie. Everyone here wastes more time in effed up code than that would ever hope to crowd in inefficiency.

If the OP doesn't care to use C++ strings, that's his decision. That doesn't make it a wise one.

Jan 29th, 2006, 10:52 AM	#11
Symptom Newbie Join Date: Sep 2005 Posts: 28 Rep Power: 0	You should use malloc to reserve space for the char array as DaWei said. Do something like (Toggle Plain Text) char message[1024]; char* begin; begin = (char) malloc (sizeof(char) (strlen(message)+1)); strncpy(begin,message,(strlen(message)+1)); char message[1024]; char* begin; begin = (char) malloc (sizeof(char) (strlen(message)+1)); strncpy(begin,message,(strlen(message)+1)); The above code copies the string inside the begin char array. You could use 2 arrays, one to store the command and one to store the argument. It's all up to you... __________________ The geeks shall inherit the earth.

Jan 29th, 2006, 11:17 AM	#13
Cache Hobbyist Join Date: Sep 2005 Posts: 266 Rep Power: 4	You don't need either malloc or new: (Toggle Plain Text) #include <iostream> using namespace std; int main () { char message[1024]; char* begin; cin.getline(message, 1024); begin = message + 4; cout << begin; cin.sync(); cin.get(); return 0; } #include <iostream> using namespace std; int main () { char message[1024]; char* begin; cin.getline(message, 1024); begin = message + 4; cout << begin; cin.sync(); cin.get(); return 0; } EDIT: Just be aware that 'begin' is pointing to the actual location of message[3]. So any changes made to 'message + 4' or above will be seen from 'begin' also. Last edited by Cache; Jan 29th, 2006 at 11:32 AM.

Jan 29th, 2006, 12:17 PM	#14
Cache Hobbyist Join Date: Sep 2005 Posts: 266 Rep Power: 4	I really wish the edit time on this forum would be extended slightly. Anyway, I just wanted to say: on reflection, it does actually look a lot cleaner to use new, and negates the need for a second variable: (Toggle Plain Text) #include <iostream> using namespace std; int main () { char message = new char[1024]; cin.getline(message, 1024); message += 4; cout << message; cin.sync(); cin.get(); delete [] message; return 0; } #include <iostream> using namespace std; int main () { char message = new char[1024]; cin.getline(message, 1024); message += 4; cout << message; cin.sync(); cin.get(); delete [] message; return 0; }

Jan 30th, 2006, 8:50 AM	#15
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	Just a possible alternative... how about using strings? string s = "say hello"; s = s.substr(5,s.length()); __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Jan 30th, 2006, 8:56 AM	#16
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Suggested in posts #7 and #12, IR, and apparently rejected . __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jan 29th, 2006, 11:11 AM	#12
nnxion Programming Guru Join Date: Jun 2005 Location: elemental plane Posts: 1,429 Rep Power: 5	I don't see why you don't use the keyword new. Or why you're not using C++ strings. __________________ "Employ your time in improving yourself by other men's writings, so that you shall gain easily what others have labored hard for." -- Socrates

Jan 30th, 2006, 9:26 AM	#17
Infinite Recursion Programming Guru Join Date: Jul 2004 Location: United States Posts: 3,467 Rep Power: 8	Missed it... I guess I read too many threads this morning... lines are running together. I should probably go get my morning supply of caffeine. __________________ http://jasonpowers.net "There are a thousand hacking at the branches of evil to one who is striking at the root."

Jan 30th, 2006, 3:32 PM	#19
Polyphemus_ Expert Programmer Join Date: Aug 2005 Location: Rotterdam, the Netherlands Posts: 942 Rep Power: 4	If you want the first 4 characters deleted, you could also do this: (Toggle Plain Text) strcmp(message, message + 4); strcmp(message, message + 4); I'm not sure this will work on every C library, since implementations can always do things weird .

Jan 30th, 2006, 3:52 PM	#20
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	strcmp is a string comparison function. Perhaps you were thinking of strcpy. Both are standard library functions. If an implementation doesn't handle them, the implementation is broken. As far as there being a time penalty for C++ strings versus char arrays, no biggie. Everyone here wastes more time in effed up code than that would ever hope to crowd in inefficiency. If the OP doesn't care to use C++ strings, that's his decision. That doesn't make it a wise one. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Application Development > C++

Char: Removing characters