Sending ctrl + z to console program

Question

I have a simple console program written in C and want to abort a text input with CTRL + Z. How is it possible?

Edit: Here is some code (untested).

#include <stdio.h>

int main()
{
    float var;

    while(1)
    {
        scanf("%lf", &var); // enter a float or press CTRL+Z

        if( ??? ) // if CTRL+Z was pressed
        {
            break;
        }

        // do something with var
    }

    printf("Job done!");

    return 0;
}

Answer 1

Basically like this:

if (fgets(buf, sizeof buf, stdin)) {
    /* process valid input */
} else {
    /* Ctrl+Z pressed */
}

There may be complications if you press Ctrl+Z in the middle of the line, but start with the basic.

---

Edit after OP was updated

You have

scanf("%lf", &var);

scanf returns the number of assignments it did. In your case, you only have 1 variable, so scanf returns 1 in the normal case or 0 when it fails. Just check the return value

int n = scanf("%lf", &var);
/* test the return value of scanf: 1 all ok; 0 no conversions; EOF: error/failure */
if (n != 1)
{
    break;
}

PS: Oh ... the specifier "%lf" in scanf requires a double, var in your program is a float. Correct that too

Answer 2

If you're using a UNIX-like operating system, ctrl-z sends a SIGSTOP, which you can generate programmatically, and catch with sigaction.

Answer 3

use signal.h to help trap the SIGTSTP sent when you hit CTRL+Z. Note that you'll want to catch SIGTSTP and not SIGSTOP as pausing is a required action for SIGSTOP by only the default action for SIGTSTP.

You may also run into problems not having scanf() return when the signal is generated. Luckily for you, that question has been asked and answered quite nicely already :) http://stackoverflow.com/questions/2512853/scanf-with-signals