getchar()

satellite · 12-23-2002, 12:10 AM

Hi everybody. I am just beginning to learn the C language.

I am having a problem with a seemingly simple script, but can't figure out why it's not working.

Code:

/* Read ordinary text a character at a time from the program's
 * stantard input, and print it with each line reversed from left to right.
 * Read until you encounter end-of-data.
 */

#include <stdio.h>  
#include <stdlib.h>    // May not need all of these
#include <string.h>

#define LIMIT 100


main(){

        int string [LIMIT];
        int i=0;
        int q;
        int total;
        for (i=0; i<LIMIT; i++){
                string[i] = getchar();
                if (string[i] == EOF ) {
                total = i;
                break;
                }
        }
        //total = i;
        for ( q=total; q >= 0; q--){
                 putchar(string[q]);
        }
return (0);
}

I've tried a bunch of stuff, and I either get nothing back, or my terminal goes all funky.

Any help would be great. Thanks

boku · 12-23-2002, 01:22 AM

change:

total = i;

to:

total = i - 1;

cyent · 12-26-2002, 02:09 PM

One thing I'm missing from that is you don't seem to even test for a new line! I would expect you would do something like...
if (string[i] == '\n') // Aha, a new line.

Be careful though, in the horrible bad world of Micro$oft new lines are a carriage return followed by a linefeed ie. a '\r' followed by '\n'

theheapWalker · 12-20-2017, 02:46 PM

another suggestion for change is just before return add a final putchar('\n');
so the prompt on the screen is clear of the reverse line of text your routine created.

Code:

      }
        //total = i;
        for ( q=total; q >= 0; q--){
                 putchar(string[q]);
        }
putchar('\n');
return (0);
}

rhubarbdog · 12-24-2017, 08:54 AM

Quote:

Originally Posted by cyent

Be careful though, in the horrible bad world of Micro$oft new lines are a carriage return followed by a linefeed ie. a '\r' followed by '\n'

Not so fopen when used on microsoft automatically strips the \r from the input stream putting them back for a write.
That's why the b-binary exists as an fopen option, useless on linux, but on microsoft leaves \r\n pairs intact

rhubarbdog · 12-24-2017, 09:04 AM

Change/add

Code:

    if(string[i]== EOF) {
      string[i]='\0';
      total=i-1;
      break;
      }

Although it doesn't matter in your example it's good practice to nul terminate your strings

rhubarbdog · 12-24-2017, 11:12 AM

You don't distinguish between no characters read, EOF being reached and 101 characters enteted. In the first and last case total hasn't been set and will lead to problems.

keefaz · 12-24-2017, 12:20 PM

Maybe he fixed the code since December 2002, who knows?

BW-userx · 12-24-2017, 02:04 PM

this gives yu a means to get out of loop

Code:

/* Read ordinary text a character at a time from the program's
 * stantard input, and print it with each line reversed from left to right.
 * Read until you encounter end-of-data.
 */

#include <stdio.h>  

#define LIMIT 100

int main()
{
	char buffer [LIMIT], c = '\0';
	int i=0;  
        
	printf("enter one letter or number\n"
	       "Then press enter\n"
	       "Enter # to end before 100\n");
	 
	while (c != '#')
	{
		c = getchar();
		buffer[i] = c;
		i++;
	}
	printf("Next\n");
	//i value has already been set
	for ( ; i > 0; i--)
		printf("%c",buffer[i]);
		      
return 0;
}

taking in one at a time, then printing out as if it is a line, is counterintuitive. Unless you read in an entire line then write it (the code) to put it into an array one char at a time, then print out the line backwards, or ...

Code:

char buffer2[100];

printf("enter a string\n");
        
getchar();
fgets(buffer2,sizeof buffer2, stdin);
b = strlen(buffer2);
	
  for (; b > 0; b--)	
	printf("%c",buffer2[b]);
		
	printf("\n");

gets a line of text then prints it out backwards.

astrogeek · 12-24-2017, 02:21 PM

Quote:

Originally Posted by keefaz

Maybe he fixed the code since December 2002, who knows?

Yes, this was a 15-year dead thread before being awakened, let's allow it to return to its repose.

BW-userx · 12-24-2017, 02:47 PM

grrrr, got duped