junk characters in char array

[lasl0w]

I have a case where I am not allowed to use the string class so I am using a char array. Does anyone have any idea why I am getting all the junk characters after my char array when i print? The input file is a 2 line file containing (no quotes) "test 1" on the first line and "test 2" on the second line.

On a related note, how can you remove chars (or remove all the contents to have the array ready for the next iteration) from a char array while maintaining the same size [80] ? I don't think the code:

str1[0] = '\0';

is doing the trick - based on my testing of multi-line input files.

#include <iostream>  
#include <sstream>  
#include <cstring>  
#include <cstdlib>  
#include <fstream>  
using namespace std;


int main ()
{
   int i, k, a, b, s, t, z, temp;
   char str1[81];
   char str2[81];
   char comp1[81];
   char comp2[81];;
   ifstream infile;

   infile.open("data.txt");
   assert(infile);

   while (infile) {
        if (infile.peek() == EOF)
           break;
        infile.getline(str1,80);
        infile.getline(str2,80);

        cout << "length of string 1 is : " << strlen(str1) << endl;
        cout << "length of string 2 is : " << strlen(str2) << endl;
        cout << str1 << endl;
        cout << str2 << endl << endl;
        s = 0;

        // Remove spaces and tabs 
        // moving to a new char array

        for (int i=0 ; i<strlen(str1) ; i++) {
           if (str1[i] != ' ' && str1[i] != '\t') {
                cout << "S equals: " << s << "I equals: " << i << endl;
                comp1[s] = str1[i];
                cout << "added a letter to comp1, incrementing S, comp1 = " << comp1 << endl;
                s++;
           }
        }
        t = 0;
        for (int k=0 ; k<strlen(str2) ; k++) {
           if (str2[k] != ' ' && str2[k] != '\t') {
                comp2[t] = str2[k];
                cout << "added a letter to comp2, incrementing T, comp2 = " << comp2 << endl;
                t++;
                cout << "T equals: " << t << "K equals: " << k << endl;
           }
        }
        cout << "comp1 length is: " << strlen(comp1) << endl;
        cout << "comp2 length is: " << strlen(comp2) << endl;
        cout << "comp1 is: " << comp1 << endl;
        cout << "comp2 is: " << comp2 << endl;

        str1[0] = '\0';
        str1[0] = '\0';
        comp1[0] = '\0';
        comp2[0] = '\0';
   }
   return 0;
}

OUTPUT:

length of string 1 is : 6
length of string 2 is : 6
test 1
test 2

S equals: 0I equals: 0
added a letter to comp1, incrementing S, comp1 = t¸Ô
S equals: 1I equals: 1
added a letter to comp1, incrementing S, comp1 = teÔ
S equals: 2I equals: 2
added a letter to comp1, incrementing S, comp1 = tes
S equals: 3I equals: 3
added a letter to comp1, incrementing S, comp1 = testÿÿÿÿB÷¿è«Ì
S equals: 4I equals: 5
added a letter to comp1, incrementing S, comp1 = test1ÿÿÿB÷¿è«Ì
added a letter to comp2, incrementing T, comp2 = taÔ
T equals: 1K equals: 0
added a letter to comp2, incrementing T, comp2 = teÔ
T equals: 2K equals: 1
added a letter to comp2, incrementing T, comp2 = teÔ
T equals: 3K equals: 2
added a letter to comp2, incrementing T, comp2 = tesÔ
T equals: 4K equals: 3
added a letter to comp2, incrementing T, comp2 = testÔ
T equals: 5K equals: 5
comp1 length is: 15
comp2 length is: 11
comp1 is: test1ÿÿÿB÷¿è«Ì"
comp2 is: testÔ"

[thelamb]

C strings are 0 terminated, you are correctly creating the chars with size 81, and copying only 80 bytes to them, but what is the value of the last char? Exactly... it is garbage data.

So, you must initialize the char array to zero, you can do this in several ways:

char test[20] = { '\0' };
char test1[20];
test1[19] = '\0';
char test2[20];
memset( test2, 0x0, 20 );

I think this also answers your second question about str[0] = '\0'; ;), if not feel free to ask more detailed questions.

[Fbody]

When you use the stream injection operator ('<<') it automatically reads through the array and outputs characters until it reaches a NULL-terminator. The extraneous/garbage characters are any characters that exist between the last char of "your" string and the first NULL that it can find.

Properly initializing and/or terminating comp1 and comp2 should correct this.

char someString[81] = {'\0'}

This will set all 81 elements of "someString" to NULL. Something like this will help, but you need to focus on being explicit about your terminating NULLs.

EDIT:
Oops, looks like thelamb beat me to it...

[lasl0w]

Thanks - that fixed my problem and I know a little more about memory management. I initialized the array to \0 then used memset at the end of each iteration to re-initialize and prepare for the next line read.