How to flush the stdin??
Why is it not working in the following code snippet?
#include <string.h>
#include <stdio.h>
#include <malloc.h>
#include <fcntl.h>
int main()
{
int i=0,j=0, sat;
char arg[256];
char * argq;
argq = malloc(sizeof(char)*10);
printf("Input the line\n");
i=read(0, arg, sizeof(char)*9);
arg[i-1]='\0';
fflush(stdin);
i=read(0, argq, sizeof(char)*5);
argq[i-1]='\0';
puts(arg);
puts(argq);
return 0;
}
Now if i give the input as 11 characters, only 9 should be read but the remaining two characters in the stdin are not flushed and read again in the argq. Why?
Input: 123 456 789
Output: 123 456 89
Why am i getting this 89 as the output?
The function fflush(stdin) is used to flush or clear the output buffer of the stream. When it is used after the scanf(), it flushes the input buffer also. It returns zero if successful, otherwise returns EOF and feof error indicator is set.
stdout. flush() forces it to “flush” the buffer, meaning that it will write everything in the buffer to the terminal, even if normally it would wait before doing so. The sys module provides functions and variables used to manipulate different parts of the Python runtime environment.
So, if the file stream is for input use, as stdin is, the behaviour is undefined, therefore it is not acceptable to use fflush() for clearing keyboard input. As usual, there are some exceptions, check your compiler's documentation to see if it has a (non-portable) method for flushing input.
I believe fflush is only used with output streams.
You might try fpurge or __fpurge on Linux. Note that fpurge is nonstandard and not portable. It may not be available to you.
From a Linux fpurge man page: Usually it is a mistake to want to discard input buffers.
The most portable solution for flushing stdin would probably be something along the lines of the following:
int c;
while ((c = getchar()) != '\n' && c != EOF);
From the comp.lang.c FAQ, see:
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With