Question

I’m trying to write a shell and I’m at the point where I want to ignore CtrlC.

I currently have my program ignoring SIGINT and printing a new line when the signal comes, but how can I prevent the ^C from being printed?

When pressing CtrlC, here is what I get:

myshell>^C myshell>^C myshell>^C 

but I want:

myshell> myshell> myshell> 

Here is my code relevant to CtrlC:

extern 'C' void disp( int sig ) {     printf('\n'); }  main() {     sigset( SIGINT, disp );     while(1)     {         Command::_currentCommand.prompt();         yyparse();     } } 

Answer 1

It’s the terminal that does echo that thing. You have to tell it to stop doing that. My manpage of stty says

* [-]ctlecho        echo control characters in hat notation (`^c') 

running strace stty ctlecho shows

ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon echo ...}) = 0 ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0 

So running ioctl with the right parameters could switch that control echo off. Look into man termios for a convenient interface to those. It’s easy to use them

#include <termios.h> #include <unistd.h> #include <stdio.h>  void setup_term(void) {     struct termios t;     tcgetattr(0, &t);     t.c_lflag &= ~ECHOCTL;     tcsetattr(0, TCSANOW, &t); }  int main() {     setup_term();     getchar(); } 

Alternatively, you can consider using GNU readline to read a line of input. As far as i know, it has options to stop the terminal doing that sort of stuff.