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printing from a C based program

Posted on 2004-11-29
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I am working on a hand held computer (bar code scanner) that can be cabled to a printer. The unit will run 'C' based programs on it. Do you have a sample 'C' program that will print say 'Hello World' to a printing device attached to the computer. I know this hardware configuration works, 'cause the vendor shipped some software (with out the source of course) that kind of does what I want, but I need to come up with my own variant. I've programmed for 20 years in Cobol, Assembler, RPGIII, Basic and VB but this is my first trip down the "C" road. I will want to eventually print bar codes to this printer, but lets cross one bridge at a time. Any suggestions will be greatly appreciated. Thanks! - ERic -
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Question by:carpetking
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by:Kent Olsen
ID: 12700108

#include <stdlib.h>
#include <stdio.h>

main ()
{
  printf (stdout, "Hello, World.\n");
}


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Expert Comment

by:Jaime Olivares
ID: 12700302
you can try to open LPT1 or PRN port as a file, then use printf(). Something like

FILE *printer;

printer = fopen("LPT1:", "wb");
if (printer) {
    fprintf (printer, "Printer test\n");
    /* some more fprintf function calls */
    fclose(printer);
} else
   printf("Error while trying to open printer port\n");
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Kent Olsen earned 1000 total points
ID: 12700510
Hi Carpetking,

Both jaime and I are speaking somewhat "tongue in cheek".  Depending on the underlying operating system, you may want to print directly to the printer, but if you're using even a quasi-mature O/S, you probably should write to a file and let the spooler handle the printing.

Most/many unix/c environments include the stream 'stdprn'.  It's not universal, but it is available in a lot of places.

As Jaime indicated, you can open a stream directly to the printer.  Be careful, the name of the device will vary with your operating system.  (Unix will probably want something like "/dev/lp" for a file name.)

Writing directly to the printer may have a serious drawback.  You'll have to make special provision for writing to the printer and handling errors.  You probably don't want your application to hang up if the printer jams.  (Then again, you might want it to hang if driving the printer is its primary function.)

Writing to a separate file and letting the spooler print the file is often the preferred method for writing to a printer.


Good Luck,
Kent
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Expert Comment

by:PaulCaswell
ID: 12703792
CarpetKing,

What kind of Barcode scanner? Ive done work with Symbol and Casio. I may be able to help with others.

Paul
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Expert Comment

by:rk_radhakrishna
ID: 12704110
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