how to use getchar() function in C?

Asked Mar 21 '13 at 20:14

Active Jul 15 '19 at 11:51

Viewed 818 times

I am trying to use a modified getchar function on a linux kernel for an operating system, to get characters from a string given from the terminal, and then print it, but every other time I call it, it seems to basically return an empty string.

kernel level space:

int sys_readchar(userptr_t chptr, it *retval) {
    char ch;
    int result;
    ch = getch();
    copyout(&ch, chptr, sizeof(ch));
    *retval=1;
    return 0;
}

user level:

int getchar(void) {
    char ch;
    int len;
    len = readchar(&ch);
    return (int)(unsigned char)ch;
}

Does anyone know what's wrong?

Thanks.

edited Jul 15 '19 at 11:51

Claudio

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asked Mar 21 '13 at 20:14

omega

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Where's the definition of the `readchar()` function? – Mar 21 '13 at 20:16
2

I'm assuming that the syntax error on `*retval=1\`` and the missing `;` after `return 0` are not in your code, right? – Shoe Mar 21 '13 at 20:16
additionally one more syntax error in `getchar()` at `len = readchar(&ch):` you puted `':'` instead of `;` – Grijesh Chauhan Mar 21 '13 at 20:19
@Uby: http://www.programmingsimplified.com/c/conio.h/getch – omega Mar 21 '13 at 20:21
1

You define `sys_readchar()` and call `readchar()`; you define `getchar()` and call `getch()`. You define `reslt` and never use it. Is this real code? – Keith Thompson Mar 21 '13 at 20:22
http://stackoverflow.com/questions/7469139/what-is-equivalent-to-getch-getche-in-linux – Grijesh Chauhan Mar 21 '13 at 20:22
their in different files, I updated the code. – omega Mar 21 '13 at 20:29

how to use getchar() function in C?

0 Answers0