john pitman wrote:
> Does anybody have any C samples handy that can do this please? I don't want
> to go to intrinsics for portability reasons...initial attempts with getc()
> don't seem to work for us.
Things to remember about C:
file streams (FILE *) are usually buffered files. Such that reads will
fill a buffer, but only return to user code that which you ask. There
are 3 choices in buffering, Full, Line, and None
(_IOFBF, _IOLBF, _IONBF).
The default for stdin is Line buffering; so you need to hit return to
complete the io of filling the buffer.
Below in the sample, I changed stdin to be No buffering. But the effect
is not what you want. It will input 1 char, and issue a newline. Then
input 1 char again -- up to the number of bytes specified.
The other sample uses "read". This appears to function as I think
you want. The functions: open, read, write, and close, I thought
were defined in stdio or stdlib.h, I had learned that they were
part of the C library.
But now, their definition is only found in unistd.h, and more
of a posix thing.
Note 1: you can set the buffering for a stream file before
any IO is done. Once done and the buffers are allocated, you
cannot change it (well, so says the documentation :) ).
Note 2: I believe you can use "read" as below while maintaining
stdin as line buffered. Allowing you both methods for input.
Keven Miller
#pragma list off
#include <stdio.h>
int main ( int ac, char *av [] )
{
int len;
char buf [256];
memset ( buf, 0, sizeof (buf));
printf ( "Prompt>" );
fflush ( stdout);
len = read ( fileno (stdin), buf, 3 );
printf ( "Read (%d) [%s]\n", len, buf );
memset ( buf, 0, sizeof (buf));
setvbuf ( stdin, NULL, _IONBF, 0 );
printf ( "Prompt>" );
fflush ( stdout);
fgets ( buf, 3+1, stdin );
len = strlen ( buf );
printf ( "fgets (%d) [%s]\n", len, buf );
}
* To join/leave the list, search archives, change list settings, *
* etc., please visit http://raven.utc.edu/archives/hp3000-l.html *
|
