shdanfor@ut-sally.UUCP (Scott Danforth) (06/13/84)
I'm using Microsoft C on a COMPAQ.
Can anybody tell me why the following C program to copy stdin to stdout
doesn't work. (If I do "cpstd < file", each line of file is printed twice.)
#include <stdio.h>
main()
{
int c;
while ((c = getc(stdin)) != EOF)
putc(c,stdout);
}dag@tellab2.UUCP (Donald Graft) (06/14/84)
The program is not performing incorrectly. Most micro-based C compilers that I am familiar with treat getc(stdin) as equivalent to getchar(). That means that characters will be echoed to the console as typed so the user can see what (s)he's doing. Since the characters are also printed by the putc(c) call, the double printing is accounted for. You need to find a call that gets characters without echoing. Most libraries provide such a call; if not, you will need to make a direct OS call. ...ihnp4!tellab1!tellab2!dag Donald Graft
jcw@cvl.UUCP (06/14/84)
>From: shdanfor@ut-sally.UUCP > >I'm using Microsoft C on a COMPAQ. >Can anybody tell me why the following C program to copy stdin to stdout >doesn't work. (If I do "cpstd < file", each line of file is printed twice.) > >#include <stdio.h> >main() >{ > int c; > while ((c = getc(stdin)) != EOF) > putc(c,stdout); >} The stdio routines for your C compiler probably use the buffered keyboard input DOS function call (INT 13?). Even if the input is being redirected, this function call echoes the lines to the screen. Your routine also writes to the screen, so that's why you get them printed twice. If you use a function call that does not echo, then when stdin is not redirected it is confusing to type. A solution would be to use IOCTL to determine if stdin is the console, and use the appropriate function call. I'm not sure if the DOS 2.0 io calls are smarter; I'll try it out. Jay Weber ..!seismo!rlgvax!cvl!jcw ..!seismo!rochester!jay jay@rochester.arpa
geller@rlgvax.UUCP (David Geller) (06/15/84)
LATTICE "C" also provides some DIRECT CONSOLE i/o functions. These
functions provided RAW or unbuffered i/o with the terminal. Their
names are:
c=getch(); int c;
putch(c);
r=ungetch(c) int r; char c;
p=cgets(s); char *p,*s;
cputs(s); char *s;
cscanf/cprintf
They are all VERY useful.
David P. Geller
Computer Consoles, Inc.
{seismo}!rlgvax!geller Office Systems Group
11490 Commerce Park Drive
Reston, VA 22091
703-648-3483