Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!bsu-cs!dhesi
From: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Newsgroups: comp.lang.c
Subject: Re: learning c
Summary: Keep portability in mind
Keywords: getchar()
Message-ID: <6487@bsu-cs.UUCP>
Date: 3 Apr 89 20:22:00 GMT
References: <1091@bnlux0.bnl.gov> <584@greens.UUCP>
Reply-To: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Distribution: usa
Organization: CS Dept, Ball St U, Muncie, Indiana
Lines: 31

In article <584@greens.UUCP> matthew@sunpix.UUCP ( Sun NCAA) writes:
>c = getchar();
>fflush(stdin);
>
>The variable 'c' will get the first character of input, and the remainder
>of the line (plus the newline) will get flushed away.

Some time ago I noticed that people were assuming that fflush() would
flush pending input data from a file open for reading.  Apparently many
implementations of stdio do this.  I don't think portable code should
rely on it.

The Turbo C 1.0 manual says fflush() on a stream open for reading
flushes the contents of the buffer.  If the stream is line-buffered the
rest of the line will indeed be flushed.

However, the 4.3BSD documentation and my (slightly outdated) System V
Interface Definition both say only that fflush() works on streams
opened for writing.  Streams open for reading are not mentioned in this
context.

     /* portably read one char and ignore rest of line */
     c = getchar();
     while (!feof(stdin) && getchar() != '\n')
	;

I don't know what the ANSI standard says, but for now it probably
doesn't matter.
-- 
Rahul Dhesi         UUCP:  <backbones>!{iuvax,pur-ee}!bsu-cs!dhesi
                    ARPA:  dhesi@bsu-cs.bsu.edu