Help on getchar Post: 302477407

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Top Forums Programming Help on getchar Post 302477407 by yg10 on Sunday 5th of December 2010 01:16:33 AM

12-05-2010

Registered User

1. getchar is an function, not a variable. So, probably you have to use getchar() instead of getchar. This explains the weird value of getchar.

2. getchar returns the integer _value_ of character entered. Casting variables compare and temp to (*char) is wrong. Just leave them as int.

3. The comparison of compare and temp will not work because characters will be analysed by program on after flushing the buffer (<ENTER> was pressed).

The following code writes characters to the file. (You need to press <ENTER> once before entering EOF - <CTRL>D in UNIX <CTRL>Z in Windows)

Code:

#include <stdio.h>

int main() {
    FILE* text;
    int temp=0;

    text=fopen("cat.txt","w+");
    while((temp = getchar()) != EOF) {
      putc(temp,text);
    }
    fclose(text);
    return(0);
}

Quote:

Originally Posted by fireblast

I wanted to make a simple program that writes chracters in a file but i didnt want to press enter .So i found the getchar which doesnt need enter.If i pass (int) getchar to putc ,in the file it shows a P character.The (int) getchar says it is equal to1734747216 so i do (int) getchar-1734747216 and it gives -62259200 and i cant understand why doesnt it give 0 and what is the P symbol since i didnt press any button?So i found that P symbol is the value of (char*)getchar and i wrote this code

Code:

#include <stdio.h>

int main()
{
FILE* text;
char* compare=(char*)getchar;
int temp=0;
text=fopen("C:\\cat.txt","w+");
while(1)
  {
  if ((char*)( temp = (int)getchar )!= compare) 
    {
      putc(temp,text);
    }
  }
  return(0);
}

Also if i change the != with == then the txt has iside it a P symbol as expected but the one with the != still doesnt work as expected
by me Smilie

yg10

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LEARN ABOUT BSD

getw

GETC(3S)																  GETC(3S)

NAME

       getc, getchar, fgetc, getw - get character or word from stream

SYNOPSIS

       #include <stdio.h>

       int getc(stream)
       FILE *stream;

       int getchar()

       int fgetc(stream)
       FILE *stream;

       int getw(stream)
       FILE *stream;

DESCRIPTION

       Getc returns the next character from the named input stream.

       Getchar() is identical to getc(stdin).

       Fgetc behaves like getc, but is a genuine function, not a macro; it may be used to save object text.

       Getw  returns  the  next  int  (a 32-bit integer on a VAX-11) from the named input stream.  It returns the constant EOF upon end of file or
       error, but since that is a good integer value, feof and ferror(3S) should be used to check the success of getw.	Getw  assumes  no  special
       alignment in the file.

SEE ALSO

       clearerr(3S), fopen(3S), putc(3S), gets(3S), scanf(3S), fread(3S), ungetc(3S)

DIAGNOSTICS

       These  functions  return  the  integer  constant EOF at end of file, upon read error, or if an attempt is made to read a file not opened by
       fopen.  The end-of-file condition is remembered, even on a terminal, and all subsequent attempts to read will return EOF until  the  condi-
       tion is cleared with clearerr(3S).

BUGS

       Because	it  is	implemented as a macro, getc treats a stream argument with side effects incorrectly.  In particular, `getc(*f++);' doesn't
       work sensibly.

7th Edition							   May 14, 1986 							  GETC(3S)