C program prints garbage values

Question

My main problem is when i run the program it not work and a runnig time error is jumping on my screen. Can someone explain me whats the problem and help me? *argv[i] is the adress and ignore the fact i don't have any free for my mallocs.

int main(int argc, char** argv)
{
FILE* file = 0;
file = fopen(argv[1], "r");
int numOfLines = countLines(file), i = 0, ch = 0, j = 0, flag = 0;
char** content;
content = (char**)malloc(numOfLines * sizeof(char*));
int* charsInLine = (int*)malloc(numOfLines * sizeof(int));
countCharsInLine(file, charsInLine);
fseek(file, 0, SEEK_SET);
for (i = 0; i < numOfLines; i++)
{
    int lenOfFile = 0;
    fseek(file, 0, SEEK_END);
    lenOfFile = ftell(file);
    content[i] = (char*)malloc(charsInLine[i] * sizeof(char) + 1);
    content = fread(content, 1, lenOfFile, file);
}
for (i = 0; i < numOfLines; i++)
{
    printf("%d string = %s", i,content[i]);
}
fclose(file);
getchar();
return 0;
}

You aren't writing anything to the `j` index that you skip, and, you are not writing a string terminator. If you want to skip characters, you need another variable to index the target string, which is only incremented when the string is written to. Perhaps the second `ch = fgetc(file);` is in the wrong place too. Just read from the file in a loop, and store in the target array. — Weather Vane, May 22 '18 at 18:04
For every malloc, there must be a free. For every fclose, there must be an fopen. Please post a Minimum Complete Verifiable Example. Look at your input, add extra printf statements to examine variables. Use a single step debugger if you can. — Pam, May 22 '18 at 18:07
I think there may be a number of flaws here depending on the input file. Please post a [mcve]. But you never reset `flag` to `0` so if you encounter `'\n'` at the expected point it will never re-enter the inner loop. — Persixty, May 22 '18 at 18:10
I have edited I'll be glad if you could check it up. @Persixty — מקס גופמן, May 22 '18 at 18:20
1., [casting malloc is bad](https://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa) 2. The second `ch = fgetc(file);` - What happens when EOF is returned? 3. Check the return value from `fopen` — Ed Heal, May 22 '18 at 18:27
@EdHeal those are basic stuff that i'll take care of. The main problem is with the initialize of the stirng. — מקס גופמן, May 22 '18 at 18:31
Why not take care of it (or not write it in the first place). BTW - There is a flaw in your algorithm with the use of the second `ch=fgetc(file);` — Ed Heal, May 22 '18 at 18:32
I'm stuck with my question those are stuff that takes a minute to make. What is the flaw? — מקס גופמן, May 22 '18 at 18:34
@EdHeal I can't upload to much code in stackoverflow but it returns the num of line. — מקס גופמן, May 22 '18 at 18:35
Are you sure that it works correctly? Does `countCharsInLine` work correctly. If both are correct you could just use `fread` instead of the loop. — Ed Heal, May 22 '18 at 18:36
Perhaps output there return values and check. Also do not forget the null character — Ed Heal, May 22 '18 at 18:40
yeah I have made + 1 in the malloc. Hoply the fread idea will work .thanks ;) — מקס גופמן, May 22 '18 at 18:42
Not a [mcve], sorry. Many, *many* small and not-so-small problems with the code, not focussing on a specific problem. — DevSolar, May 22 '18 at 18:50
@DevSolar My main problem is when i run the program it not work and a runnig time error is jumping on my screen. — מקס גופמן, May 22 '18 at 18:53
Yes, but you shrug off lots of good advice, telling us "that's not where the problem is", and we're staring at *lots* of issues with your code that a "correct" answer *would all have to address because you didn't*. Please check again what [mcve] means. Especially the "minimal". This is debugging 101. Also, ref. [Machete Debugging](https://rootdirectory.ddns.net/dokuwiki/doku.php?id=software:machetedebugging) if the MCVE text is too long. — DevSolar, May 22 '18 at 18:55
@DevSolar - I agree - correcting those small mistakes goes a long way to getting a correct solution. Just ignoring them is not playing cricket — Ed Heal, May 22 '18 at 19:09

Ed Heal · Accepted Answer · 2018-05-22T23:44:59.177

1

I am going to assume countLines and countCharsInLine works correctly

Here is the updated code with comments

int main(int argc, char** argv)
{
   FILE* file fopen(argv[1], "r");
   if (file == NULL) {
      // Output some error message
      return EXIT_FAILURE;
   }

   int numOfLines = countLines(file); // I assume this rewinds.

   char** content;
   content = malloc(numOfLines * sizeof(char*)); // Do not need a cast

   int* charsInLine = malloc(numOfLines * sizeof(int));

   countCharsInLine(file, charsInLine);

   rewind(file); // Easier to read the fseek

   for (int i = 0; i < numOfLines; i++)
   {
      content[i] = malloc(charsInLine[i] + 1); // * sizeof(char) - Do not need this as sizeof(char) is defined as 1
      // Reading one item of size charsInLine[i]
      if (fread(content[i], charsInLine[i], 1, file) != 1) {
         // Some error has occurred
         fclose(file);
         return EXIT_FAILURE; 
      }
      content[i][charsInLine[i]] = 0; // Add null character

      int ch = fgetc(file);
      if (ch != '\n' && ch != EOF) { // Should be reading either the new line at the end of the line, or EOF
         // Some error has occurred
         fclose(file);
         return EXIT_FAILURE; 
      }
   }
   fclose(file);
   // Should free up the stuff that is malloced - I leave that up to you
   return EXIT_SUCCESS;
}

edited May 22 '18 at 23:44

answered May 22 '18 at 18:55

Ed Heal

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i didnt understand the part of the if fread what does it mean != 1 – מקס גופמן May 22 '18 at 19:00
Please read the manual page for `fread` - i.e [fread](https://linux.die.net/man/3/fread) – Ed Heal May 22 '18 at 19:01
Ok and what about if I want to split between the files like the first for 4 chars goes to the first index and so on? – מקס גופמן May 22 '18 at 19:03
1

Do not understand the question? Anyway - that is more that enough help for now – Ed Heal May 22 '18 at 19:04
I mean that i want to get the first 4 chars in content[0] next 4 in content[1] and so on – מקס גופמן May 22 '18 at 19:06
That is a different problem. – Ed Heal May 22 '18 at 19:07
@מקסגופמן - does the above code work? if so please accept it – Ed Heal May 22 '18 at 19:34
1

Typo, missing square bracket: *content[i][charsInLine[i]] = 0; // Add null character*, but otherwise thanks for setting a good example for this asker. – Pam May 22 '18 at 21:19

C program prints garbage values

1 Answers1