Clearing a String

How can I clear a string? and not just by making all the characters spaces.

Thanks

Quote:

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Originally posted by Jperensky
How can I clear a string? and not just by making all the characters spaces.

Thanks

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Do you mean like the whole screen?? If so then clr() will do it!

Or,

Code:

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std::string str = "Now is the time...";
std::cout << str << std:endl;
str = " ";

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This assumes, of course, that your string variable is named 'str'. Now, if it's named 'Rover'... ;)

Note that your compiler will probably insist that you put a 'space' character between the quotes.

-Skipper

Assuming this is a std::string you can simply say:

str.erase();

If it's a C string you'll have to define "empty" better, for most uses doing this will cause the string to become empty:

str[0] = '\0';

-Prelude

Hi,
Do you mean a string std::string or an array of char's?

To clear an array of char's so that C sees an empty string just make the first element 0(zero).


char mystr[20] = "this is a test";
printf("\n%s",mystr); //prints this is a test

mystr[0] = 0;

printf("\n%s",mystr); //prints only the '/n'

Hope this helps.

its generally better to assign the element of the string to NULL rather than zero

>its generally better to assign the element of the string to NULL rather than zero
If you mean the nul character '\0' then I agree. If you mean the NULL macro defined in cstdio I would like to know why you think so.

-Prelude

Quote:

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Originally posted by iain
its generally better to assign the element of the string to NULL rather than zero

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Look at the definition of NULL (_null.h) and you'll be surprised :).

I am using an array of chars not std::string and I tried _null.h but I am programming this to work under Linux so that isn't working.

I am looping threw a text file char by char storing each char to the next available spot (or cell) in the array once it reads a \n char it stops and I can process the string (array of chars) after that I need to "reset the string." The problem I am having is I can't get the string to clear. So when I rewrite over the char array if anyline previously stored was longer than anyone after I have the extra char(s) after the string (line) I am working with.

*Example*

The text file contains:
this is line one
and line 2
also 3

I am getting this when I print it to screen:
this is line one
and line 2 one
also 3ne 2 one

Anyone have a solution?

There is a function called strset() defined in string.h.
e.g.#include<string.h>
strset(samplestring,0);
This will set all characters in the string samplestring to the NULL character with the ASCII value 0.

Quote:

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Originally posted by Jperensky
I am using an array of chars not std::string and I tried _null.h but I am programming this to work under Linux so that isn't working.

I am looping threw a text file char by char storing each char to the next available spot (or cell) in the array once it reads a \n char it stops and I can process the string (array of chars) after that I need to "reset the string." The problem I am having is I can't get the string to clear. So when I rewrite over the char array if anyline previously stored was longer than anyone after I have the extra char(s) after the string (line) I am working with.

*Example*

The text file contains:
this is line one
and line 2
also 3

I am getting this when I print it to screen:
this is line one
and line 2 one
also 3ne 2 one

Anyone have a solution?

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You copy the string into the buffer one char at a time?
That explains it. After you have copied all characters, add a '\0' character last. This is a NULL terminator, meaning the string ends there (not showing up the rest of the junk from the previous string).

When I append a '\0' char to the end of the array all I can see is the last char in the string... it is the correct char though.

Source:

Code:

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#include <iostream.h>
#include <fstream.h>
#include <stdio.h>
#include <string.h>



void main()

{

      ifstream OpenFile("text.txt");
      char ch, temp_str[50];
      int cord = 0, reset = 0;
      while(!OpenFile.eof())

      {

            OpenFile.get(ch);
           
              if (ch == '\n') {
                  cord++;
                  temp_str[cord] = '\0';
                  cout<<temp_str<<"\n";                 
              }               
              else {
                  temp_str[cord] = ch;
                  cord++; 
              } 
              reset = 0;
              cord = 0;

      }

      OpenFile.close();
     
      cout<<temp_str;

}

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You set the index to 0 in every loop, so you will never get further than the first element.

Quote:

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Originally posted by Jperensky

Code:

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OpenFile.get(ch);
           
if (ch == '\n')
{
  cord++;
  temp_str[cord] = '\0';
  cout<<temp_str<<"\n";                 
}               
else
{
  temp_str[cord] = ch;
  cord++; 
} 

reset = 0;
cord = 0;

---

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You said I set the index to '\0'. I set the last char in the string to '\0' as I was instructed to do in a previous post. How should I do it?

You should move the cord = 0; to the if statement:

Code:

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if (ch == '\n') {
  cord++;
  temp_str[cord] = '\0';
  cout<<temp_str<<"\n";                 
  cord = 0;
}               
else {
  temp_str[cord] = ch;
  cord++; 
} 
reset = 0;

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If you read a newline character you display the string and reset the index (cord) to 0. Now you can read the next line starting at the beginning of your string.

This should work:

Code:

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#include <iostream.h>
#include <fstream.h>
#include <stdio.h>
#include <string.h>



void main()

{

      ifstream OpenFile("text.txt"); // Your text file.
      char ch, temp_str[50];
      int cord = 0, last_count = 0;
      while(!OpenFile.eof())

      {

            OpenFile.get(ch);
           
              if (ch == '\n') {
                  temp_str[cord] = '\0';
                  cout<<temp_str<<"\n"; /* Instead of printing it to your console you could process it however before preceding. */
                  cord = 0;
                  last_count = 0;                 
              }               
              else {
                  temp_str[cord] = ch;
                  cord++;
                  last_count++; 
              }

      }

      OpenFile.close();
      last_count = last_count - 1;
      temp_str[last_count] = '\0';
      cout<<temp_str<<endl; /* Same as line 23 (to process the current string) just for the last line in the text file since there is no '\n' at the end of the line. */

}

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Quote:

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Originally posted by Staz
void main()

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Eh...

*quietly walking away, avoiding the wraith of some of the older members here...*

>*quietly walking away, avoiding the wraith of some of the older members here...*

Any two, or three, in particular who come to mind? :D

* curled up in foxhole awaiting 'incoming' *

-Skipper

Quote:

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Originally posted by Staz

...

int main()

...

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