MS-DOS, save data from COM1: to file and display on console at the same time

Question

I have a MS-DOS 3.22 laptop that will receive simple text data over serial COM1.

I can make it save to file by doing TYPE COM1 >> data.log and I can make it show the data on the console with TYPE COM1 >> CON but I can't do this simultaneously as the TYPE COM1 is a never ending command.

Is there a way for me to both display the COM data on my console and to save it to file simultaneously?

thx!

Answer 1

The ideal tool for this is some DOS version of the Unix tee command; once you have that,

TEE data.log < COM1

will read data from the first serial port and write it to both data.log and the screen.

DOS versions of tee are available from a variety of sources:

• 4DOS (a replacement shell) includes a built-in TEE command;
• Ian Stewartson’s Unix utilities include TEE in part D;
• I see Garbo has a few other implementations, which I haven’t tried (or don’t remember using).

(Other, Unix-style uses of TEE won’t have the same immediate effect under DOS since programs can’t run simultaneously: TYPE COM1 | TEE data.log would fail because under DOS, pipes work by redirecting the output to a temporary file, waiting for the command feeding the pipe to finish, then running the next command with its input redirected from the temporary file.)

Answer 2

I do not know of any command or app to do as you ask. Instead I would use Borland Turbo C++ and code it myself... Its been ages I code something for MS-DOS so I am not confident to do it for you. But you're in luck I found something in my C++ archives I coded back in the days and will help I think:

//---------------------------------------------------------------------------
//--- Includes: -------------------------------------------------------------
//---------------------------------------------------------------------------
#include <iostream.h>
//----------------------------------------------------------------------------
//--- Global data: -----------------------------------------------------------
//----------------------------------------------------------------------------
typedef unsigned char byte;
typedef unsigned int word;
word far *memw=0x00000000;
byte far *mem=0x00000000;
char    key;
word    keyhi;

word    com;
//----------------------------------------------------------------------------
//--- I/O: -------------------------------------------------------------------
//----------------------------------------------------------------------------
void inkey()
    {
    key=0;
    keyhi=0;
    asm {
        mov ax,256
        int 0x16
        jz  esc
        mov ax,0
        int 0x16
        mov key,al
        mov keyhi,ax
        }
esc:
    }
//---------------------------------------------------------------------------
void inkeyw()
    {
    asm {
        mov ax,0
        int 0x16
        mov key,al
        mov keyhi,ax
        }
    }
//---------------------------------------------------------------------------
byte in(word adr)
    {
    byte    x;
    asm {
        mov dx,adr
        in  al,dx
        mov x,al
        }
        return x;
    }
//---------------------------------------------------------------------------
void out(word adr,byte x)
    {
    asm {
        mov dx,adr
        mov al,x
        out dx,al
        }
    }
//---------------------------------------------------------------------------
//--- com: ------------------------------------------------------------------
//---------------------------------------------------------------------------
void com_init(word x)
    {
    com=memw[(0x400>>1)+x-1];   // COM IO address from DOS TAB 0000:0400h
    out(com+1,0);           // no interrupts
    out(com+3,3);           // 1 start, 8 data, 1 stop, 0 parity
    }
//---------------------------------------------------------------------------
void com_speed(word f)
    {
    word x,h,l;
    x=115200/f;
    h=(x >> 8) & 255;
    l=x & 255;
    x=in(com+3) & 127;
    out(com+3,x+128);
    out(com+0,l);
    out(com+3,x+128);
    out(com+1,h);
    out(com+3,x);
    }
//---------------------------------------------------------------------------
byte com_in()
    {
    byte s;
//  do s=in(com+5); while ((s&1)!=1);
    s=in(com+0);
    return s;
    }
//---------------------------------------------------------------------------
void com_out(byte d)
    {
    byte s;
    do s=in(com+5); while ((s&32)!=32);
    out(com+0,d);
    }
//---------------------------------------------------------------------------
//--- Subroutines: ----------------------------------------------------------
//---------------------------------------------------------------------------
void couthex(word x)
    {
    word    a,i;
    char    c;

    for (i=0;i<4;i++)
        {
        a=(x >> 12) & 15;
        x=x << 4;
        if (a<10) c=a+'0';
        if (a>=10) c=a-10+'A';
        cout << c;
        }
    cout << 'h';
    }
//---------------------------------------------------------------------------
//--- Main: -----------------------------------------------------------------
//---------------------------------------------------------------------------
void main()
    {
    asm {
        mov ax,3
        int 0x10
        }

    char    x=0;

    com_init(1);
    com_speed(9600);        // set to speed used by source device
    cout << "COM adress = "; couthex(com);  cout << endl;

    do      {
        inkey();
        x=com_in(); // this reads 1 BYTE from COM
        couthex(x); // this write it as hex on screen
        cout << endl;
        } while (keyhi==0);


    cout << "COM adress = "; couthex(com);  cout << endl;
    inkeyw();

    }
//---------------------------------------------------------------------------
//--- End. ------------------------------------------------------------------
//---------------------------------------------------------------------------

So you just modify the main loop to write the BYTE x as a character and also store to some file.

I am not sure if on such old MS-DOS version is the configuration table in the same place so you might set the COM IO address manually.

if you do not have turbo C++ just google it its still being used in some schools so it should not be any problem finding it. Here first link I found by google just now:

• Turbo C++

IIRC I used 3.2.2.0 version on MS-DOS 6.22. As you want older MS-DOS then older version of C may be required too...

File access is also a common practice assignment so there should be no problem finding any examples of it but just in case:

//============================================================================
//=== includes: ==============================================================
//============================================================================
#include <iostream.h>
#include <fstream.h>
#include <ctype.h>
//============================================================================
//=== main: ==================================================================
//============================================================================
void main()
    {
    // IIRC this just clears screen into 80x25 text mode
    asm {
        mov ax,3
        int 16
        }

    ofstream out;
    out.open("some_file_name.txt",ios::out);
    out << "some text" << endl; // endl adds CR,LF
    out.close();

    // IIRC this just clears screen into 80x25 text mode and clears keyboard buffer
    asm {
        mov ax,0
        int 0x16
        mov ax,3
        int 16
        }
    }
//============================================================================
//=== end. ===================================================================
//============================================================================