C/C++ :: Copying A String From A Pointer To New Pointer
Mar 4, 2015
I need to make a copy of a string that is defined by char *full and copy it into a different pointer defined by char *duplicate. I have written code to do this however it will not work and i cannot figure it out my code is as follows:
char *duplicate = (char *)malloc(strlen(full) + 1);
strcpy(duplicate, full); /*Make second version of full*/
char *Ptr = strtok(duplicate, "
"); /*Split duplicate up*/
I have a full program written but i know this is where the problem is because i have used printf statements to see where the program fails. I get no errors and it compiles successfully but it hits this point of the program and it just stops and windows automatically shuts down the program.
char *full is pointing to:
"To be, or not to be? That is the question:
Whether 'tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles,"
I need to duplicate the string because i need to use strtok but i will need the original string later on so i need an unaltered version.
const void insertStuff(const void *key, const int value){ // I want to convert the void pointer into one // of three types of pointers(int, string, or double) switch(value){ case 0: int *intPtr = key;
[Code] .....
But this causes an error of: "crosses initialization of int*intPtr"
I was having problems changing the value of my head node I passed it as an argument as head which would be the address. The parameter was defined as struct node *head. like this
I tried manipultaing pointer values to change head node value but it did not work. I saw some code online which used pointer to pointers(in code below) to change head node value it worked I dont fully understand why. Would like better understanding of why.
Would also like to know why the argument call needed &head instead of just head.
remove = deleteNode(&head,found); opposed to remove = deleteNode(head,found);
I have to write a program to print pascals triangle and stores it in a pointer to a pointer , which I am not entirely sure how to do. I also have to write the file and read it, then create a binary file. Assignment is attached. I am not the best with programming and especially with pointers. I will post my code below.
Code: #include <stdio.h> #include <stdlib.h> void writePascalTriangle(char *fileName, int heightOfTriangle, int **triangle) { FILE *fp; fp=fopen("writePascalTriangle.txt", "w");
I'm making a system like twitter for class called ShoutOut.com I want to be able to get the PublicShoutOut pointer pointed to by the start iterator and assign it to firstShoutOutToDisplay and secondShoutOutToDisplay because I need that in order to pass the pointers to one of my functions. When I step through the debugger the values in start are all default values like "" and so are the values in this->firstShoutOutToDisplay but the message that start points to is being output just fine.
EDIT: got rid of irrelevant code. Am I using the correct syntax to do this?
if (start != finish) { //getting these because a shoutout needs to be passed to the function that displays //options for a shoutout this->firstShoutoutToDisplay = (*start);
i have been fiddling with pointers but I don't understand how the proper syntax is written when I want to acces an element of an array through a pointer to a pointer...The code is all mostly just random bs for learning purposes. I marked the problem "// THIS LINE"
This is a sample program that declares a Matrix as a structure with an array as a pointer to a pointer. The following program is supposed to store a matrix in the structure "_Matrix" and later print the matrix just entered but it fails giving me a "segmentation fault". The sample code is given below
Code: #include <stdio.h> #include <stdlib.h> struct _Matrix { int row_size; int col_size; int **mat;
i really don't know why has a error in my code, that pass a pointer of pointer (name of a matrix with 2 dimensions). Here is the source code of a simple example where appears segmentation fault when execute (but compiles normal):
#include <stdio.h> #define LINHAS 3 #define COLUNAS 5 float a[LINHAS][COLUNAS]; void zeros(float **p,float m, float n){ int i,j; for(i=0;i<m;i++)
I wish to know how to traverse or loop through a dynamic 2D array using pointer to pointer as returned by the code above. Like I would in a static T[20][20] 2D array.
What I want is basically to assign to the *p the pointer of the string so that i could do the following printf(" print string %s",*p); so i dont know how to do that.
1. The debugger shows that the characters are entered into the word pointer, and when a punctuation or space character is encountered, I terminate the string with a ''. But when I use puts to print the string, garbage is printed. Why is this?
2. Also, if I don't allocate memory for word the compiler gives a warning about it being used uninitialised. But I didn't allocate memory for the array of pointers(words), and the compiler didn't give any warnings. Whats the difference between a pointer and an array of pointers?
In another forum, this example code fragment was stated as being an example of undefined behavior. My understanding is that a literal string exists from program start to program termination, so I don't see the issue, even though the literal string is probably in a different part of memory.
Code: /* ... */ const char *pstr = "example"; /* or even */ char *pstr = "example"; /* as long as no attempt is made to modify the data pointed to by pstr, */ /* unless pstr is later changed to point to a stack or heap based string */
how string literal that works with the cin object?
char * str = "This is a string constant";
Is the str stored the address of the first character of the string literal?
But some books just state that the pointer-to-char (char pointer) stores the address of the string literal". So just wonder how it is.
When it is used with cout, cout just treats it like a string and instead of printing the address, it just prints out all characters one by one until it reaches the terminated null character.
If this is the case, then I am just wondering how cin works with it? with a statement like this cin >> str; ?
Does the computer allocate enough memory for it? and then cin stores the first character into the first address and then advances to the next address and stores the next character?
then the cstrp can be treated as cstra, and so I can also use
cin>>cstrp;
but when I write the following program, I find it don't work, don't have clue
#include <iostream> #include <string> #include <cstring> using namespace std; int main() { char cstr[5];
[Code] ....
for cstr, it work exactly as what I expected, but for cstrp, no matter what I input, with a null terminator or not, I just got nothing printed. why? can we really use cstrp in that way or not? How to use it?
Ok, I'm having a few problems with strings, mostly string functions saying they're not able to compare a string with a char pointer.
int main() { int counter = 0; int x, y, z;
[Code].....
My goal is to take in a command and store it in a string. Different commands have different amounts of information I need. One command is "new flight <flightnumber> <seats available>". First, I try to understand which command is being asked, using the first character to decide. Once I can assume which command is being attempted, I try to separate the string into smaller strings (words) using strtok. I then compare the words that should be constant (new and flight), to make sure the command is syntactically correct (which I use strcmp for). Then I'll go on to create a new flight, which is a class that takes in a char * and integer (which is why I need to convert a char * to integer).
Dynamic memory allocation and pointer arithmetic with char arrays.
The class was given to me in a very basic skeleton form with prototypes but no implementations, along with a test function to test my implementations. I CAN NOT use any C String functions in this assignment.
The part of the program which is troubling is the append function, which just appends a parameter string215 object to the end of the current string215 object.
// Add a suffix to the end of this string. Allocates and frees memory. void string215::append(const string215 &suffix) { char *output = new char[str_len(data)+suffix.length()+1]; for(int x = 0; x < str_len(data); x++) { *output = *data;
[Code]...
This portion of the code is tested in the 13th test of the test function as shown here:
string215 str("testing"); ...
// Test 13: test that append works in a simple case. curr_test++; string215 suffix("123"); str.append(suffix); if (strcmp(str.c_str(), "testing123") != 0) { cerr << "Test " << curr_test << " failed." << endl; failed++; }
Here is the description of the append class: Add the suffix to the end of this string. Allocates a new, larger, array; copies the old contents, followed by the suffix, to the new array; then frees the old array and updates the pointer to the new one.
My program aborts at the very end of the append function execution with the error message:
I know there is strtok() to do the tokenization;but all strtok() examples I have seen only output one token at a time, moving the pointer ahead. Can't the tokens be saved somewhere?
I am trying to read the string from user and the allocate it to the another string which is ptr string but not successful . Do I have to use any dynamic memory allocation here?
Code: int main(){ char test[5]; char *strng, *base; int i; base=strng; for(i=0; i<4; i++){
