Segmentation Error - c++

Question

I am trying to implement my own shell in Linux. I take input from the user and parse it. But it gives segmentation error while I copy my tokens in a array. I am unable to solve this issue.
Here is the code I implemented
#include <iostream>
#include <sys/wait.h>
#include <unistd.h>
#include <string.h>
using namespace std;
int main ()
{
char * input;
string insert;
cout<<"My Shell $";
getline(cin,insert);
input= new char [insert.size()+1];
strcpy(input, insert.c_str());
char * token;
char * parsed[100];
int count;
token=strtok(input, " ");
while (token!=NULL)
{
strcpy(parsed[count],&(token[count]));
count++;
token=strtok(NULL, " ");
}
}

Answer 1

#include <string.h>
No.
If you want the C functions, use <cstring>, which puts them in the std:: namespace.
But you don't want the C functions, you want C++ <string>. Believe me, you do.
using namespace std;
I'll let that pass for the example's sake. Get out of that particular habit in any production code.
getline(cin,insert);
Good. You're ready to do C++.
input= new char [insert.size()+1];
strcpy(input, insert.c_str());
Bad. You just tied your hands to your back.
char * parsed[100];
An array of 100 pointers to char. Just the pointers, uninitialized, pointing nowhere.
int count;
Uninitialized.
token=strtok(input, " ");
C. shudder....
strcpy(parsed[count],&(token[count]));
Undefined behaviour. count is not initialized, and even if it does happen to be between 0 and 99, parsed[count] still does not point to valid memory, so copying something to it will do bad things.
Besides, your token is at token, not at token[count]...
count++;
Adding 1 to uninitialized is UB, and still uninitialized. ;-)
}
You forgot to delete [] input.
Let me suggest a different, more C++-ish approach, that will still give you your array of pointers to each token (if you insist on that):
getline( cin, input );
// turn spaces to null bytes
std::replace( input.begin(), input.end(), ' ', '\0' );
// need an additional one for the finds below to work
input.append( '\0' );
// vector takes away all of that manual memory management
std::vector< char * > parsed;
size_t i = 0;
// skip leading (ex-) spaces
while ( ( i = input.find_first_not_of( '\0', i ) ) != std::string::npos )
{
// push the pointer to the token on the vector
parsed.push_back( input.data() + i );
// skip to end of token
i = input.find( '\0', i );
}
At this point, parsed is a vector of char * to the tokens in input (at least, as long as input itself is still in scope). You can check its size with parsed.size(), and access it as "naked" array with parsed.data(), although I am sure you will find the vector more convenient.
If you don't want to keep input around, replace
std::vector< char * > parsed;
with
std::vector< std::string > parsed;
and
parsed.push_back( input.data() + i );
with
parsed.push_back( std::string( input.data() + i ) );
and you have a copy of the tokens in your vector.
That is still pretty rough handling, mind you, since even spaces inside of quotation marks will be detected as "end of token", but at least it's C++, none of that C string handling.

Answer 2

You didn't initialize the variable count, and its value is undefined(may be very large, so the program will fail reading from memory). You should use int count = 0;.
And the elements in the array parsed isn't initialized and does not point to allocated memory. The behavior of your call to strcpy is also undefined. Add parsed[count] = new char[strlen(token) + 1]; before your call to strcpy. Don't forget to use delete after everything is done.
At last, I think you didn't use strtok properly. Why did you use &(token[count])? Maybe you should replace it with token.

Answer 3

Variable int count is undefined, in means it can be random value, change it to int count = 0;

Answer 4

Just initialize your count variable to 0

Answer 5

Please try to use this code. I tried in VS2010 and it is working fine now.
#include <iostream>
#include <string.h>
#include <string>
using namespace std;
int main (void)
{
char* input = NULL;
string insert;
cout<<"My Shell $";
/* getline(cin, insert);*/
std::getline(cin, insert);
input= new char[insert.size() + 1];
strcpy(input, insert.c_str());
char* token = NULL;
char* parsed[100] = {0};
int count = 0;
token = strtok(input, " ");
while ( token != NULL)
{
parsed[count] = token;
count++;
token = strtok(NULL, " ");
}
for ( int index = 0; index<count; index++ )
{
cout << parsed[index] << std::endl;
}
system("pause");
return 0;
}

Answer 6

Please try the below code #
#include <iostream>
#include <unistd.h>
#include <string.h>
using namespace std;
int main (void)
{
char* input = NULL;
string insert;
cout<<"My Shell $";
getline(cin, insert);
input= new char[insert.size() + 1];
strcpy(input, insert.c_str());
char* token = NULL;
char* parsed[100];
for (int index = 0; index < 100; index++)
{
parsed[index] = NULL;
}
int count = 0;
token = strtok(input, " ");
while ( token != NULL)
{
strcpy(parsed[count], &(token[count]));
count++;
token = strtok(NULL, " ");
}
return 0;
}