Unbuffered char reads from App from stdin (keyboard)

Unbuffered char reads from App from stdin (keyboard)

[Steven Vacca]

App and Linux kernel 2.2.13 running on mpc860T.

I would like to know the best way, from inside my GNU C App,
to sense if there's a keyboard key pressed.  Something
similar to kbhit() in Microsoft C.  I would like to have a particular
thread execute a loop continuously and only when a key
is present, do a getc() or getchar(), or gets(), and the like.

What is the best way to accomplish this?
Is there a way to make stdin unbuffered?

Thanks,

ShutEyeThinkin

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

Re: Unbuffered char reads from App from stdin (keyboard)

[Wolfgang Denk]

In message <01C1B608.E92871A0.svacca@valcom.com> you wrote:
>
> App and Linux kernel 2.2.13 running on mpc860T.
>
> I would like to know the best way, from inside my GNU C App,
> to sense if there's a keyboard key pressed.  Something

man select

man termios (search for VMIN and VTIME)

Wolfgang Denk

--
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd@denx.de
See us @ Embedded Systems Nuremberg, Feb 19-21, Hall 12 K01 (with TQ)

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RE: Unbuffered char reads from App from stdin (keyboard)

[Steven Vacca]

Mark,

Using some of your unbuf_getch() code inside a while (1)
loop, fgetc() still blocks until a '\n', then, with each iteration
of the loop, 1 char is returned from the fgetc() until all chars are
returned, then fgetc() blocks again.

Is there a way to get chars without blocking and waiting for
the '\n'?

Thanks,

ShutEyeThinkin





//*************************************************************************
***********
Mark's code:

Hi,

I found some examples on groups.google.com that I modified
to suite my needs.  Try something like these:

int
unbuf_getch()
{
    FILE    *input;
    int      selected;
    struct termios initial_settings;
    struct termios new_settings;

    if (!isatty(fileno(stdout))) {
        fprintf(stderr,"You are not a terminal, OK.\n");
    }

    input = fopen("/dev/tty", "r");
    if(!input) {
        fprintf(stderr, "Unable to open /dev/tty\n");
        exit(1);
    }

    tcgetattr(fileno(input),&initial_settings);
    new_settings = initial_settings;
    new_settings.c_lflag &= ~ICANON;
    new_settings.c_lflag &= ~ECHO;
    new_settings.c_cc[VMIN] = 1;
    new_settings.c_cc[VTIME] = 0;
    new_settings.c_lflag &= ~ISIG;
    if(tcsetattr(fileno(input), TCSANOW, &new_settings) != 0) {
        fprintf(stderr,"could not set attributes\n");
    }
    selected = fgetc(input);
    tcsetattr(fileno(input),TCSANOW,&initial_settings);

    fclose(input);
    return selected;
}

int
kbhit()
{
   int ret, c;
   fd_set read_file_descr;
   struct timeval timeout;
   int debug_flag;

   /* this could be a global */
   debug_flag = 0;

   /* this macro initializes the file descriptor read_file_descr to to be
the empty set */
   FD_ZERO(&read_file_descr);

   /* this macro adds fileno(stdin) to the file descriptor read_file_descr
*/
   FD_SET(fileno(stdin), &read_file_descr);

   timeout.tv_sec = 0;
   timeout.tv_usec = 100;
   /* int FD_SETSIZE  macro is maximum number of filedescriptors that fd_set
can hold */
   /* function select waits for specified filedescr. to have a signal */
   /* last argument struct timeval *timeout */
   ret = select(1, &read_file_descr, NULL, NULL, &timeout);
   switch( ret ) /* 0 is timeout, -1 error (in errno), 1 = data */
   {
      case -1:
         if( debug_flag )
            fprintf(stdout, "select returned -1 error\n");
         ret = 0;
         break;
      case 0:
         if( debug_flag )
            fprintf(stdout, "select returned 0 timeout\n");
         ret = 0;
         break;
      case 1:
         if( debug_flag )
            fprintf(stdout, "SELECT returned=%d input\n", ret);
         ret = 1;
         break;
      default:
         if( debug_flag )
            fprintf(stdout, "select returned=%d invalid\n", ret);
         break;
   }

   /* test if user has data.  this'll eat the first non-CR keys pressed */
   if( FD_ISSET(fileno(stdin), &read_file_descr) )
   {
      c = getc(stdin);
      if( debug_flag )
         fprintf(stdout, "USER KEY=%d\n", c);
      FD_CLR(fileno(stdin), &read_file_descr);
   }

   return ret;
}

Mark
--
[root@hjinc mclayton] /sbin/insmod stddisclaimer.o


> -----Original Message-----
> From: Steven Vacca [mailto:svacca@valcom.com]
> Sent: Friday, February 15, 2002 10:10 AM
> To: LinuxEmbeddedMailList (E-mail)
> Subject: Unbuffered char reads from App from stdin (keyboard)
>
>
>
> App and Linux kernel 2.2.13 running on mpc860T.
>
> I would like to know the best way, from inside my GNU C App,
> to sense if there's a keyboard key pressed.  Something
> similar to kbhit() in Microsoft C.  I would like to have a particular
> thread execute a loop continuously and only when a key
> is present, do a getc() or getchar(), or gets(), and the like.
>
> What is the best way to accomplish this?
> Is there a way to make stdin unbuffered?
>
> Thanks,
>
> ShutEyeThinkin
>
>

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

RE: Unbuffered char reads from App from stdin (keyboard)

[Rick Hunnicutt]

Just do a read on STD_IN (fd of 0) of one char...

#define STD_IN 0
char ch;

    read(STD_IN, &ch, 1)


> -----Original Message-----
> From: owner-linuxppc-embedded@lists.linuxppc.org
> [mailto:owner-linuxppc-embedded@lists.linuxppc.org]On Behalf Of Steven
> Vacca
> Sent: Friday, February 15, 2002 10:39 AM
> To: LinuxEmbeddedMailList (E-mail)
> Subject: RE: Unbuffered char reads from App from stdin (keyboard)
>
>
>
> Mark,
>
> Using some of your unbuf_getch() code inside a while (1)
> loop, fgetc() still blocks until a '\n', then, with each iteration
> of the loop, 1 char is returned from the fgetc() until all chars are
> returned, then fgetc() blocks again.
>
> Is there a way to get chars without blocking and waiting for
> the '\n'?
>
> Thanks,
>
> ShutEyeThinkin
>
>
>
>
>
> //************************************************************
> *************
> ***********
> Mark's code:
>
> Hi,
>
> I found some examples on groups.google.com that I modified
> to suite my needs.  Try something like these:
>
> int
> unbuf_getch()
> {
>     FILE    *input;
>     int      selected;
>     struct termios initial_settings;
>     struct termios new_settings;
>
>     if (!isatty(fileno(stdout))) {
>         fprintf(stderr,"You are not a terminal, OK.\n");
>     }
>
>     input = fopen("/dev/tty", "r");
>     if(!input) {
>         fprintf(stderr, "Unable to open /dev/tty\n");
>         exit(1);
>     }
>
>     tcgetattr(fileno(input),&initial_settings);
>     new_settings = initial_settings;
>     new_settings.c_lflag &= ~ICANON;
>     new_settings.c_lflag &= ~ECHO;
>     new_settings.c_cc[VMIN] = 1;
>     new_settings.c_cc[VTIME] = 0;
>     new_settings.c_lflag &= ~ISIG;
>     if(tcsetattr(fileno(input), TCSANOW, &new_settings) != 0) {
>         fprintf(stderr,"could not set attributes\n");
>     }
>     selected = fgetc(input);
>     tcsetattr(fileno(input),TCSANOW,&initial_settings);
>
>     fclose(input);
>     return selected;
> }
>
> int
> kbhit()
> {
>    int ret, c;
>    fd_set read_file_descr;
>    struct timeval timeout;
>    int debug_flag;
>
>    /* this could be a global */
>    debug_flag = 0;
>
>    /* this macro initializes the file descriptor
> read_file_descr to to be
> the empty set */
>    FD_ZERO(&read_file_descr);
>
>    /* this macro adds fileno(stdin) to the file descriptor
> read_file_descr
> */
>    FD_SET(fileno(stdin), &read_file_descr);
>
>    timeout.tv_sec = 0;
>    timeout.tv_usec = 100;
>    /* int FD_SETSIZE  macro is maximum number of
> filedescriptors that fd_set
> can hold */
>    /* function select waits for specified filedescr. to have
> a signal */
>    /* last argument struct timeval *timeout */
>    ret = select(1, &read_file_descr, NULL, NULL, &timeout);
>    switch( ret ) /* 0 is timeout, -1 error (in errno), 1 = data */
>    {
>       case -1:
>          if( debug_flag )
>             fprintf(stdout, "select returned -1 error\n");
>          ret = 0;
>          break;
>       case 0:
>          if( debug_flag )
>             fprintf(stdout, "select returned 0 timeout\n");
>          ret = 0;
>          break;
>       case 1:
>          if( debug_flag )
>             fprintf(stdout, "SELECT returned=%d input\n", ret);
>          ret = 1;
>          break;
>       default:
>          if( debug_flag )
>             fprintf(stdout, "select returned=%d invalid\n", ret);
>          break;
>    }
>
>    /* test if user has data.  this'll eat the first non-CR
> keys pressed */
>    if( FD_ISSET(fileno(stdin), &read_file_descr) )
>    {
>       c = getc(stdin);
>       if( debug_flag )
>          fprintf(stdout, "USER KEY=%d\n", c);
>       FD_CLR(fileno(stdin), &read_file_descr);
>    }
>
>    return ret;
> }
>
> Mark
> --
> [root@hjinc mclayton] /sbin/insmod stddisclaimer.o
>
>
> > -----Original Message-----
> > From: Steven Vacca [mailto:svacca@valcom.com]
> > Sent: Friday, February 15, 2002 10:10 AM
> > To: LinuxEmbeddedMailList (E-mail)
> > Subject: Unbuffered char reads from App from stdin (keyboard)
> >
> >
> >
> > App and Linux kernel 2.2.13 running on mpc860T.
> >
> > I would like to know the best way, from inside my GNU C App,
> > to sense if there's a keyboard key pressed.  Something
> > similar to kbhit() in Microsoft C.  I would like to have a
> particular
> > thread execute a loop continuously and only when a key
> > is present, do a getc() or getchar(), or gets(), and the like.
> >
> > What is the best way to accomplish this?
> > Is there a way to make stdin unbuffered?
> >
> > Thanks,
> >
> > ShutEyeThinkin
> >
> >
>


** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

RE: Unbuffered char reads from App from stdin (keyboard)

[Steven Vacca]

FYI (For Y'all's Info):

Here's what I've done.

I wanted to check if 1 or more keys have been pressed, and if so,
get just the next available key in the buffer.
I then wanted to process that key before echoing it to the
terminal, if at all, for nth-degree of control.

- I used termios to disable console Cannonical mode and Echoes.
- I used fcntl() to make stdin Non_Blocking, since, if there's no
  key in the buffer, read() will block.
- I then use:

	read(0,&key,1);

to read just the next key, without blocking when there is no key
in the buffer.


ShutEyeThinkin




-----Original Message-----
From:	Steven Vacca [SMTP:svacca@valcom.com]
Sent:	Friday, February 15, 2002 10:10 AM
To:	LinuxEmbeddedMailList (E-mail)
Subject:	Unbuffered char reads from App from stdin (keyboard)

App and Linux kernel 2.2.13 running on mpc860T.

I would like to know the best way, from inside my GNU C App,
to sense if there's a keyboard key pressed.  Something
similar to kbhit() in Microsoft C.  I would like to have a particular
thread execute a loop continuously and only when a key
is present, do a getc() or getchar(), or gets(), and the like.

What is the best way to accomplish this?
Is there a way to make stdin unbuffered?

Thanks,

ShutEyeThinkin

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/