Some questions about linux termios

Some questions about linux termios

[pei lin]

Hi,buddy
   I am puzzled by the linux termios.
    First Question about /dev/tty0 and /dev/tty,this two devices is
the same one?
    When i am in X terminal,as /dev/pts/0 , i do "echo hello >
/dev/pts/0 and echo hello > /dev/tty ", they return the same like that
"hello" on the screen .This means /dev/tty ->/dev/pts/0? But "echo
hello > /dev/tty0",there is nothing on the screen.And when i go to
Init 3 mode ,like /dev/tty1,when i do "echo hello > /dev/tty1 and echo
hello > .dev/tty and echo hello > /dev/tty0" ,They return the same all
print hello on the screen.Do they all point to the /dev/tty1?

    The second Question is that i write a small program to get
keyboard input like below.When i run it in X terminal ,when i press
keyboard it can return but can not get the press and release event.And
in the console,like tty1,it doesn't work .i don't know why.

file : get_keyboard.c

#include <stdio.h>
#include <linux/keyboard.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <linux/kd.h>
#include <termios.h>
#include <unistd.h>
int main()
{
	int fd,len,i;
	struct kbentry entry;
	unsigned char buf[64];
	struct termios  ts,old_ts;	
	char * path;
	path = ttyname(0);
	printf("%s!\n",path);
	fd = open(path, O_RDONLY|O_NOCTTY);
	if(fd < 0){
		printf("open the device error!\n");
	}
	
	printf("fd --- %d!\n",fd);
	
	if (ioctl( fd, KDSKBMODE, K_RAW ) < 0) {
			printf("set mode wrong!\n");
	}
	

	tcgetattr( fd, &old_ts );
	

	   ts = old_ts;
     ts.c_cc[VTIME] = 0;
     ts.c_cc[VMIN] = 1;
     ts.c_lflag &= ~(ICANON|ECHO|ISIG);
     ts.c_iflag = 0;
     tcsetattr( fd, TCSAFLUSH, &ts );

     tcsetpgrp( fd, getpgrp() );


	   entry.kb_table = K_NORMTAB;
     entry.kb_value = 0;
	
	while(1){
		len=read(fd,buf,64);
  	printf("len ========= %d!\n",len);
		for(i =0; i < len;i++){
			entry.kb_index = buf[i];
			if(ioctl(fd,KDGKBENT,&entry)){
			printf("struct entry :%d %d
%d\n",entry.kb_table,entry.kb_index,entry.kb_value);
			if('2' == entry.kb_index){
				tcsetattr( fd, TCSAFLUSH, &old_ts );
				exit(0);
			   }
			}
                                      }
		}
}

Re: Some questions about linux termios

[Jonathan Isom]

in Sat, Jul 12, 2008 at 12:24 PM, pei lin <telent998@gmail.com> wrote:
> Hi,buddy
>   I am puzzled by the linux termios.
>    First Question about /dev/tty0 and /dev/tty,this two devices is
> the same one?
>    When i am in X terminal,as /dev/pts/0 , i do "echo hello >
> /dev/pts/0 and echo hello > /dev/tty ", they return the same like that
> "hello" on the screen .This means /dev/tty ->/dev/pts/0? But "echo
> hello > /dev/tty0",there is nothing on the screen.And when i go to
> Init 3 mode ,like /dev/tty1,when i do "echo hello > /dev/tty1 and echo
> hello > .dev/tty and echo hello > /dev/tty0" ,They return the same all
> print hello on the screen.Do they all point to the /dev/tty1?

/dev/tty is a pointer to the current tty. whether it be /dev/tty1 or
/dev/pts/0.  when you login you are assigned a tty and if you
don't know it you can just use /dev/tty and it will open the current
tty

>    The second Question is that i write a small program to get
> keyboard input like below.When i run it in X terminal ,when i press
> keyboard it can return but can not get the press and release event.And
> in the console,like tty1,it doesn't work .i don't know why.
>
> file : get_keyboard.c
>
> #include <stdio.h>
> #include <linux/keyboard.h>
> #include <sys/ioctl.h>
> #include <fcntl.h>
> #include <linux/kd.h>
> #include <termios.h>
> #include <unistd.h>
> int main()
> {
>        int fd,len,i;
>        struct kbentry entry;
>        unsigned char buf[64];
>        struct termios  ts,old_ts;
>        char * path;
>        path = ttyname(0);
>        printf("%s!\n",path);
>        fd = open(path, O_RDONLY|O_NOCTTY);
>        if(fd < 0){
>                printf("open the device error!\n");
>        }
>
>        printf("fd --- %d!\n",fd);
>
>        if (ioctl( fd, KDSKBMODE, K_RAW ) < 0) {
>                        printf("set mode wrong!\n");
>        }
>
>
>        tcgetattr( fd, &old_ts );
>
>
>           ts = old_ts;
>     ts.c_cc[VTIME] = 0;
>     ts.c_cc[VMIN] = 1;
>     ts.c_lflag &= ~(ICANON|ECHO|ISIG);
>     ts.c_iflag = 0;
>     tcsetattr( fd, TCSAFLUSH, &ts );
>
>     tcsetpgrp( fd, getpgrp() );
>
>
>           entry.kb_table = K_NORMTAB;
>     entry.kb_value = 0;
>
>        while(1){
>                len=read(fd,buf,64);
>        printf("len ========= %d!\n",len);
>                for(i =0; i < len;i++){
>                        entry.kb_index = buf[i];
>                        if(ioctl(fd,KDGKBENT,&entry)){
>                        printf("struct entry :%d %d
> %d\n",entry.kb_table,entry.kb_index,entry.kb_value);
>                        if('2' == entry.kb_index){
>                                tcsetattr( fd, TCSAFLUSH, &old_ts );
>                                exit(0);
>                           }
>                        }
>                                      }
>                }
> }
> --
> To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>