In c, how do I continuously print text out until the user enters a specific character?

Question

I want to print out text (from a file previously opened) until I press the key q. All of the methods I have tried pause my text being printed out. Is there a way to print the text while looking for a key press in C?

ex:

//after turning off canonical mode and echoing

char* output = "press q to stop this";

char ch;

while(ch = getchar()!= 'q')
{
    printf("%s\n",output);
}

It only prints the prompt after you enter a char. I want it to continue to print the prompt continuously.

Solved my problem with this webpage that I found: http://cc.byexamples.com/2007/04/08/non-blocking-user-input-in-loop-without-ncurses/

http://stackoverflow.com/questions/21197977/how-can-i-prevent-scanf-to-wait-forever-for-an-input-character — lu5er, Apr 08 '17 at 18:16
I found this webpage and I was able to solve my problem with it. [link](http://cc.byexamples.com/2007/04/08/non-blocking-user-input-in-loop-without-ncurses/) — joeGV, Apr 08 '17 at 20:19

score 1 · Answer 1 · answered Apr 08 '17 at 17:59

1

You can create a child process.

parent prints elem from file
child waiting user input
to stop execution you can use kill(getppid(), SIGTERM) to kill parent and exit(0) to kill child

answered Apr 08 '17 at 17:59

Lluís M.

80
6

Might be worth a mention of threads too – tijko Apr 08 '17 at 18:03
@tijko In my opinion, in this case, is easier with a child process. – Lluís M. Apr 08 '17 at 18:05
because of the way I'm getting the text I want to print out I don't think I can easily use a child process. Is there a way to do this outside of a child process? – joeGV Apr 08 '17 at 18:14
@joeGV you can use select to stdin – Lluís M. Apr 08 '17 at 18:20

score 0 · Answer 2 · edited May 23 '17 at 12:25

Based on jave.web's response in Wait for input for a certain time

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include<unistd.h>
#include<windows.h>


char waitForCharInput( int seconds ){
    char c = '_'; //default return
    while( seconds != 0 ) {
        if( _kbhit() ) { //if there is a key in keyboard buffer
            c = _getch(); //get the char
            break; //we got char! No need to wait anymore...
        }

        Sleep(1000); //one second sleep
        --seconds; //countdown a second
    }
    return c;
}

int main()
{
    FILE *fp = fopen("_filename_","r");
    char buffer[255];
    while(fgets(buffer, 255, (FILE*) fp))
    {
        printf("%s\n", buffer);
        char response = waitForCharInput(1);
        if(response == 'q')
            break;
    }
}

score 0 · Accepted Answer · answered Apr 08 '17 at 20:21

0

Found my answer here: http://cc.byexamples.com/2007/04/08/non-blocking-user-input-in-loop-without-ncurses/

I understand my question was too broad but this is how I solved my issue.

answered Apr 08 '17 at 20:21

joeGV

9
2

In c, how do I continuously print text out until the user enters a specific character?

3 Answers3