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Full Discussion: Read input from another tty
Top Forums Shell Programming and Scripting Read input from another tty Post 302686459 by bakunin on Tuesday 14th of August 2012 03:28:19 PM
Old 08-14-2012
You haven't said which OS, etc., you are on, so you might have to adapt the following a bit:

In principle every device in Unix/Linux has a "device file", which resides in /dev. In the case of a terminal this is most probably /dev/ttyX, where "X" is some number and the device file is a character device. For instance, from my Ubuntu system:

Code:
# ls -l /dev/tty*
crw-rw-rw- 1 root tty     5,  0 Aug 14 08:35 /dev/tty
crw--w---- 1 root root    4,  0 Aug 14 08:35 /dev/tty0
crw------- 1 root root    4,  1 Aug 14 08:36 /dev/tty1
crw--w---- 1 root tty     4, 10 Aug 14 08:35 /dev/tty10
crw--w---- 1 root tty     4, 11 Aug 14 08:35 /dev/tty11
[...etc. ...]

Reading from such a device will give you whatever a user sitting at this terminal types, writing to such a device will produce the output at that screen. So, after making sure you are allowed to write to and read from the terminals device file you could probably direct your <stderr> output to it by

Code:
/some/process 2>/dev/ttyX

I hope this helps.

bakunin
 

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LEARN ABOUT MOJAVE

ports

ports(1M)                                                 System Administration Commands                                                 ports(1M)

NAME

       ports - creates /dev entries and inittab entries for serial lines

SYNOPSIS

       /usr/sbin/ports [-r rootdir]

DESCRIPTION

       devfsadm(1M) is now the preferred command for /dev and /devices and should be used instead of ports.

       The  ports  command  creates symbolic links in the /dev/term and /dev/cua directories to the serial-port character device files in /devices
       and adds new entries in /etc/inittab for non-system ports found.  System-board ports are given single lower-case letters for names (such as
       a and b) while other ports are named numerically.

       ports  searches the kernel device tree to find the serial devices attached to the system. It also checks /dev/term and /dev/cua to see what
       symbolic links to serial devices already exist. ports then performs the following:

       1.  Assigns new numbers (or letters for system-board ports) to ports that are attached to the system but do not have /dev/term and /dev/cua
           entries. The numbers or letters assigned are the lowest-unused numbers or letters.

       2.  Removes dangling links: links from /dev/term and /dev/cua pointing to no-longer-existing ports.

       3.  Creates new /dev/term and /dev/cua links for new serial devices.

       4.  Invokes sacadm(1M) to make new port monitor entries for the new devices. This is not done automatically for on-board ports; on worksta-
           tions these ports are often not used for dial-in sessions, so a port-monitor for one of these ports must be created explicitly.

       If the configuration has not changed, ports exits without doing anything.

   Notice to Driver Writers
       ports considers devices with a node type of DDI_NT_SERIAL, DDI_NT_SERIAL_MB, DDI_NT_SERIAL_DO, or DDI_NT_SERIAL_MB_DO  to  be  serial  port
       devices.  Devices  with  one  of  these node types must create minor device names that obey the following conventions when calling ddi_cre-
       ate_minor_node(9F).

         o  The minor name for non-system port devices (DDI_NT_SERIAL) consists of an ASCII numeric string, where the first port on the device  is
            named 0, the second named 1, the third named 2, up to the number of ports provided by the device.

         o  The  minor  name for non-system dialout devices (DDI_NT_SERIAL_DO) is the ASCII numeric port name, concatenated with ,cu. For example,
            the minor name for the first dialout port on the serial board is 0,cu.

         o  The minor name for system-board port devices (DDI_NT_SERIAL_MB) consists of a string containing a single  ASCII  lowercase  character,
            where the first port on the device is named a, the second is named b, the third is named c, for all ports on the device (or up through
            port z).

         o  The minor name for system-board dialout devices (DDI_NT_SERIAL_MB_DO) consists of the lowercase character port name, concatenated with
            ,cu. For example, the minor name for the first dialout port on the on-board serial device is a,cu.

       To  prevent  disks  from attempting to automatically generate links for a device, drivers must specify a private node type and refrain from
       using one of the above node types when calling ddi_create_minor_node(9F).

OPTIONS

       The following options are supported:

       -r rootdir      Causes ports to presume that the /dev/term, /dev/cua, and /devices directories are found under rootdir, not directly  under
                       /. If this argument is specified, sacadm(1M) is not invoked, since it would update terminal administration files under /etc
                       without regard to the rootdir.

EXAMPLES

       Example 1: Creating the Serial and Dialout Minor Device Nodes

       The following example creates the serial and dialout minor device nodes from the xkserial driver's attach(9E) function:

       /*
       * Create the minor number by combining the instance number
       * with the port number.
       */ #define XKNUMPORTS           8
       #define XKMINORNUM(i, p)     ((i) << 4 | (p))
       #define XKMINORNUM_DO(i, p)  ((i) << 4 | (p) | 0x80)
       int
       xkserialattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
       {
          int instance, portnum;
          char name[8];
              /* other stuff in attach... */
          instance = ddi_get_instance(dip);
          for (portnum = 0; portnum < XKNUMPORTS; portnum++) {
              /*
               * create the serial port device
               */
               sprintf(name, "%d", portnum);
               ddi_create_minor_node(dip, name, S_IFCHR,
                  XKMINORNUM(instance, portnum), DDI_NT_SERIAL, 0);

               /*
                * create the dialout device
                */
                sprintf(name,"%d,cu", portnum);
                ddi_create_minor_node(dip, name, S_IFCHR,
                    XKMINORNUM_DO(instance, portnum), DDI_NT_SERIAL_DO, 0);
            }
       }

       Example 2: Installing the xkserial Port Driver on a Sun Fire 4800

       The following example installs the xkserial port driver on a Sun Fire 4800 (with the driver  controlling  the  fictional  XKSerial  8  port
       serial board), with these special files in /devices:

       # ls -l /devices/ssm@0,0/pci@18,700000/pci@1/xkserial@f,800000/
       crw-r-----   1 root sys   32,  16 Aug 29 00:02 xkserial@2000:0
       crw-r-----   1 root sys   32, 144 Aug 29 00:02 xkserial@2000:0,cu
       crw-r-----   1 root sys   32,  17 Aug 29 00:02 xkserial@2000:1
       crw-r-----   1 root sys   32, 145 Aug 29 00:02 xkserial@2000:1,cu
       crw-r-----   1 root sys   32,  18 Aug 29 00:02 xkserial@2000:2
       crw-r-----   1 root sys   32, 146 Aug 29 00:02 xkserial@2000:2,cu
       crw-r-----   1 root sys   32,  19 Aug 29 00:02 xkserial@2000:3
       crw-r-----   1 root sys   32, 147 Aug 29 00:02 xkserial@2000:3,cu
       crw-r-----   1 root sys   32,  20 Aug 29 00:02 xkserial@2000:4
       crw-r-----   1 root sys   32, 148 Aug 29 00:02 xkserial@2000:4,cu
       crw-r-----   1 root sys   32,  21 Aug 29 00:02 xkserial@2000:5
       crw-r-----   1 root sys   32, 149 Aug 29 00:02 xkserial@2000:5,cu
       crw-r-----   1 root sys   32,  22 Aug 29 00:02 xkserial@2000:6
       crw-r-----   1 root sys   32, 150 Aug 29 00:02 xkserial@2000:6,cu
       crw-r-----   1 root sys   32,  23 Aug 29 00:02 xkserial@2000:7
       crw-r-----   1 root sys   32, 151 Aug 29 00:02 xkserial@2000:7,cu

       /dev/term contain symbolic links to the serial port device nodes in /devices

       # ls -l /dev/term
       /dev/term/0 -> ../../devices/[....]/xkserial@2000:0
       /dev/term/1 -> ../../devices/[....]/xkserial@2000:1
       /dev/term/2 -> ../../devices/[....]/xkserial@2000:2
       /dev/term/3 -> ../../devices/[....]/xkserial@2000:3
       /dev/term/4 -> ../../devices/[....]/xkserial@2000:4
       /dev/term/5 -> ../../devices/[....]/xkserial@2000:5
       /dev/term/6 -> ../../devices/[....]/xkserial@2000:6
       /dev/term/7 -> ../../devices/[....]/xkserial@2000:7

       and /dev/cua contain symbolic links to the dialout port device nodes in /devices

       # ls -l /dev/cua

       /dev/cua/0 -> ../../devices/[....]/xkserial@2000:0,cu
       /dev/cua/1 -> ../../devices/[....]/xkserial@2000:1,cu
       /dev/cua/2 -> ../../devices/[....]/xkserial@2000:2,cu
       /dev/cua/3 -> ../../devices/[....]/xkserial@2000:3,cu
       /dev/cua/4 -> ../../devices/[....]/xkserial@2000:4,cu
       /dev/cua/5 -> ../../devices/[....]/xkserial@2000:5,cu
       /dev/cua/6 -> ../../devices/[....]/xkserial@2000:6,cu
       /dev/cua/7 -> ../../devices/[....]/xkserial@2000:7,cu

FILES

       /dev/term/n     Logical serial port devices

       /dev/cua/n      Logical dialout port devices

       /etc/inittab

       /etc/saf/*

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE         |      ATTRIBUTE VALUE        |
       +-----------------------------+-----------------------------+
       |Availability                 | SUNWcsu                     |
       +-----------------------------+-----------------------------+

SEE ALSO

       add_drv(1M), devfsadm(1M), drvconfig(1M), pmadm(1M), sacadm(1M), attributes(5), devfs(7FS), attach(9E), ddi_create_minor_node(9F)

       Writing Device Drivers

SunOS 5.10                                                          8 Nov 2002                                                           ports(1M)
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