Getchar() is ignored by my program

Hi,

I am testing a program where I am doing some FILE I/O manipulations. At the end of the program I use a getchar() just to leave the console open. However, the program ignores the getchar and closes the console at once (not leaving me observe the results).

I am only putting the main.c. Sorry for the incomprehensible names of the variables:)

Do you have any ideas?
Thanks

Code:

---

int main(void)
{
        int sfalma;
        typos_stoivas stoiva; //stoiva twn orwn
        float oros1,oros2,apotelesma;
        char symbolo, apantisi, metathematiki[256];
        int i;

    FILE *fp;
               
    if ( (fp=fopen("input.txt","r"))==NULL )
    {
      printf("Error opening file\n");
      exit(1);                                                                                         
    } 
   
    while (!feof(fp))       
    {       
          dimiourgia(&stoiva);
          metathematiki[0]='\0';
          i=0;

          while ( (symbolo = (char) fgetc(fp))!= '\n')
                {
                        metathematiki[i]=symbolo;
                        i++;
                        if (symbolo >= '0' && symbolo <= '9') //bre8hke oros
                        {
                                apotelesma = (float)(symbolo-'0');
                                othisi(&stoiva,apotelesma,&sfalma);
                        }
                        else if ( einai_telestis(symbolo) ) //bre8hke telesths
                        {
                                if (symbolo == '!')            // An einai paragontiko tote prepei na bgaloyme ena
                {                              // stoixeio apo ti stoiva
                  PopValue(stoiva,&oros1,&sfalma);
                  PopState(&stoiva,&sfalma);
                  apotelesma = (float) paragontiko((int)oros1);
                                  othisi(&stoiva,apotelesma,&sfalma);                                                 
                }
                                else
                {
                  PopValue(stoiva,&oros2,&sfalma);
                  PopState(&stoiva,&sfalma);
                  PopValue(stoiva,&oros1,&sfalma);
                  PopState(&stoiva,&sfalma);
                  apotelesma = upologismos(symbolo,oros1,oros2);
                  othisi(&stoiva,apotelesma,&sfalma);
                }   
                        }
                } // first while
       
    metathematiki[i]='\0';
    PopValue(stoiva,&apotelesma,&sfalma);
    PopState(&stoiva,&sfalma);
    printf("%s=%5.2f\n",metathematiki,apotelesma);
    }        // second while

    fclose(fp);
    getchar();
    return 0;
}

---

Possibly it is crashing prior to that.

There is a way to set VS to leave the console open so you don't have to use getchar(). Don't ask me what it is, but it would certainly be a better idea than all the "getchar()" nonsense people use at the end of their code. Can't you open a terminal into the compile directory, compile and run from there? It also makes much more sense to retain the output from each run, rather than having to open a new window each time, then closing it, etc.

Meh, more code indented with a mix of spaces and tabs, resulting in an eyesore when posted.

Code:

---

int main(void)
{
  int sfalma;
  typos_stoivas stoiva; //stoiva twn orwn
  float oros1,oros2,apotelesma;
  char symbolo, apantisi, metathematiki[256];
  int i;

  FILE *fp;
 
  if ( (fp=fopen("input.txt","r"))==NULL )
  {
    printf("Error opening file\n");
    exit(1);                                                                                         
  } 
 
  while (!feof(fp))       
  {       
    dimiourgia(&stoiva);
    metathematiki[0]='\0';
    i=0;

    while ( (symbolo = (char) fgetc(fp))!= '\n')
    {
      metathematiki[i]=symbolo;
      i++;
      if (symbolo >= '0' && symbolo <= '9') //bre8hke oros
      {
        apotelesma = (float)(symbolo-'0');
        othisi(&stoiva,apotelesma,&sfalma);
      }
      else if ( einai_telestis(symbolo) ) //bre8hke telesths
      {
        if (symbolo == '!')            // An einai paragontiko tote prepei na bgaloyme ena
        {                              // stoixeio apo ti stoiva
          PopValue(stoiva,&oros1,&sfalma);
          PopState(&stoiva,&sfalma);
          apotelesma = (float) paragontiko((int)oros1);
          othisi(&stoiva,apotelesma,&sfalma);                                                 
        }
        else
        {
          PopValue(stoiva,&oros2,&sfalma);
          PopState(&stoiva,&sfalma);
          PopValue(stoiva,&oros1,&sfalma);
          PopState(&stoiva,&sfalma);
          apotelesma = upologismos(symbolo,oros1,oros2);
          othisi(&stoiva,apotelesma,&sfalma);
        }   
      }
    } // first while
   
    metathematiki[i]='\0';
    PopValue(stoiva,&apotelesma,&sfalma);
    PopState(&stoiva,&sfalma);
    printf("%s=%5.2f\n",metathematiki,apotelesma);
  }        // second while

  fclose(fp);
  getchar();
  return 0;
}

---

> while (!feof(fp))
This will NEVER be true, at the same time as this being false
> while ( (symbolo = (char) fgetc(fp))!= '\n')

feof() is a STATE (of a past event), not a prediction of a future action.

The file I read in the program, consists of many lines ending in a newline character.

My program works fine for all of these lines...I get the correct mathematical results for each line.

Whenever I find a newline character, I make the calculations and then reenter the main while loop.

The problem is that after reading the last line' s last character which is again a newline, the program should make the calculations and then find EOF. This could cause a close of file and a waiting for another carriage return from the keyboard.

Do you think that my program fails to realize when this EOF comes?
So, it never loops out?

The getchar() can be ignored or "skipped", if there is a newline in the keyboard buffer.

add this line, just in front of your getchar line of code, for "industrial strength" holding the console text window, open:

Code:

---

while((ch = getchar()) != '\n');
//your getchar() line goes here

---

now, instead of getchar() just taking one char, it will take all the char's up to (and including), the first newline.

Then your getchar() line should hold the console window open.

If you have input numerous newlines at once, into your keyboard buffer, then you should remove them in a loop, of course.

As far as I can see, it will never exit.

> while ( (symbolo = (char) fgetc(fp))!= '\n')
If this loop exits, then feof() will be still be false, because there are no more reads from the file in between.

> while ( (symbolo = (char) fgetc(fp))!= '\n')
If this loop finds EOF, then it will loop forever; Having reached EOF, you've blown your chance of ever getting a \n to get you out of the loop.

Personally, I would suggest this approach

Code:

---

// read a whole line
while ( fgets( metathematiki, sizeof(metathematiki), fp ) != NULL ) {
  int i = 0;
  // examine each character on the line
  for ( i = 0 ; metathematiki[i] != '\0'; i++ ) {
    symbolo = metathematiki[i];
    // more stuff
  }
}

---

I wrote a simple program to check how I can get out of the loop and it works.
However, I guess that there will be smarter ways to do this...

Code:

---

#include <stdio.h>

int main(void) {
   
FILE *fp;
char ch;

    if ((fp=fopen("input.txt","r")) == NULL) {
        printf("The file cannot be opened\n");
        exit(1);
    } //end if
           
    while (!feof(fp)) {

        while ( (ch = getc(fp)) !='\n') {
          fputc(ch,stdout);         
        } //end while - checking the newline character

        fputc('\n',stdout);
        if ((ch=getc(fp))!=EOF) fputc(ch,stdout);
        else break;     
     
    } //end while - checking for end of file     
         
    getchar();
    fclose(fp);
   
    return 0;
   
} //end main

---