How to Read Stdin Without Waiting for Enter C
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How exercise check the stdin without stopping?
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How do check the stdin without stopping?How do bank check the stdin without stopping?(OP) ok, this is my problem. I'm running an space loop where i am gathering data and writing information technology to a file. I desire to exist able to cheque the stdin then the user tin input 'q' or something like that so suspension the loop. The problem is that scanf(), getchar(), getc(), etc end the loop and look for the user to press "Enter". is in that location anyhow of checking the stdin without stopping the plan? Please Help. Scarlet Flag SubmittedThank you for helping keep Tek-Tips Forums gratuitous from inappropriate posts. |
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Source: https://www.tek-tips.com/viewthread.cfm?qid=371103
RE: How do check the stdin without stopping?
It depends on what OS you lot are using.
1) DOS/Windows - use kbhit or _kbhit. Information technology lives in conio.h and volition tell you whether the user has hitting the keyboard or not. If the user has hit the keyboard then you can exercise a getch otherwise continue looping.
2) Unix - use pthreads: create ii threads: 1 to poll the keyboard and one to do your continuous loop
3) Any other OS - I haven't got a inkling.
RE: How exercise check the stdin without stopping?
Example of using pthreads with a polling loop. This is written with a C++ compiler and then in that location may exist $.25 that practice not compile with C.
#include <pthread.h>
#include <stdio.h>
struct Mutual
{
bool mRunning; /* Tells u.s.a. when to quit */
float mCount;
};
/* The number crunching bit */
void* Cruncher (void* info)
{
struct Common* cptr = (struct Common*) info;
cptr->mCount = 0.0;
while (cptr->mRunning)
{
cptr->mCount++;
}
return (void*) 0;
}
void* PollKbd (void* info)
{
struct Mutual* cptr = (struct Common*) info;
int ch;
printf ("Printing q followed by return to quit\due north");
practise {
ch = getchar ();
} while (ch != 'q');
cptr->mRunning = false;
render (void*) 0;
}
principal ()
{
pthread_t crunchThread, pollThread;
struct Mutual common = { true, 0.0 };
pthread_create (&pollThread, 0, PollKbd, &mutual);
pthread_create (&crunchThread, 0, Cruncher, &common);
pthread_join (pollThread, 0);
pthread_join (crunchThread, 0);
printf ("Count got up to %f\n", mutual.mCount);
render 0;
}
RE: How do check the stdin without stopping?
fork the job
child writes to files
father reads stdin, cease child if got 'q'
or what always you lot want
voice clamantis in deserto.
RE: How do cheque the stdin without stopping?
The posix thread solution seems okay.
A quicker, easier solution might be to check the input
queue to see if anything'south available.
This curt example just increments a counter until
the user presses a 'q' and <enter>.
Usually, the input will be in "cooked" mode, and so
whatever is typed will not exist available for reading
until the <enter> is pressed. And then suddenly everything
is fabricated bachelor. If the input is in "raw" (or "cbreak")
fashion, so each character is fabricated available as it's typed.
Utilise the stty command to endeavour that before running it.
This is a posix thing, for Linux and the like. This detail
instance was tested on a Solaris eight car.
Hope that helps!
-BUD
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/filio.h>
main( int c, char *five[])
{
int numAvailable;
char buf[100];
int counter;
for( counter = 0; ; ++counter) {
sleep( 1);
fprintf( stdout, "%d\due north", counter);
/*
* encounter if anything is bachelor on the input queue
*/
if( ioctl( 0, FIONREAD, &numAvailable) < 0) {
fprintf( stderr, "ioctl failed: %south\n", strerror( errno));
break;
}
/*
* input awaits - a read won't block now
*/
if( numAvailable <= 0)
continue;
/*
* one wouldn't typically use read.
*/
if( read( 0, buf, sizeof buf) <= 0) {
fprintf( stderr, "read failed: %s\due north", strerror( errno));
break;
}
/*
* as long equally the standard input is in normal "cooked"
* mode, the read call will never return 1; at that place will
* always be at least one more byte bachelor, the '\north'.
* Null is bachelor for reading until the user
* presses return.
*/
if( buf[0] == 'q') {
fprintf( stderr, "Quit.\n");
break;
}
}
}
RE: How exercise cheque the stdin without stopping?
I always wondered what the Unix equivalent of kbhit was. Cheers BigUglyDude.