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Full Discussion: C, UNIX: How to redirect 'stdout' to a file from a C code?
Top Forums Programming C, UNIX: How to redirect 'stdout' to a file from a C code? Post 302983597 by jim mcnamara on Thursday 13th of October 2016 03:52:41 PM
Old 10-13-2016
Here is sample code using dup() and dup2()- I copied this from somewhere years ago:
Code:
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, const char *argv[])
{
    int out = open("cout.log", O_RDWR|O_CREAT|O_APPEND, 0600);
    if (-1 == out) { perror("opening cout.log"); return 255; }

    int err = open("cerr.log", O_RDWR|O_CREAT|O_APPEND, 0600);
    if (-1 == err) { perror("opening cerr.log"); return 255; }

    int save_out = dup(fileno(stdout));
    int save_err = dup(fileno(stderr));

    if (-1 == dup2(out, fileno(stdout))) { perror("cannot redirect stdout"); return 255; }
    if (-1 == dup2(err, fileno(stderr))) { perror("cannot redirect stderr"); return 255; }

    puts("doing an ls or something now");

    fflush(stdout); close(out);
    fflush(stderr); close(err);

    dup2(save_out, fileno(stdout));
    dup2(save_err, fileno(stderr));

    close(save_out);
    close(save_err);

    puts("back to normal output");

    return 0;
}

From your description it does not sound like this will help you.
These 2 Users Gave Thanks to jim mcnamara For This Post:
alex_5161 kbw
 

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LEARN ABOUT DEBIAN

hpset

HPSET(1)							       LOCAL								  HPSET(1)

NAME

     hpset -- printer commands

SYNOPSIS

     hpset [-hco] [commands ...]

DESCRIPTION

     hpset is used to send commands to a printer. These commands are synonyms for ESC Codes based on the PCL standard from Hewlet Packard.

Options
     -c      redirect output to stdout

     -oname  redirect output into the specified file or device redirect

     -h      prints a help message

Commands
     back    Puts every setting back to the printer defaults.

     test    Starts the self test.

     out     If paper is inside the printer it will be thrown out.

     cr      activates the linefeed

     lbon    acivates the linebreak.

     leftright
	     forces the printer to print only from left to right.

     rightleft
	     forces the printer to print only from right to left.

     bidirect
	     forces the printer in both ways.

     execoff
	     The following commands are not executed but printed.

     execon  The following commands are executed.

     nice    High quality printing.

     econo   Enables fast and economic printing.

     landscape
	     Printing in landscape format.

     portrait
	     Printing in portrait format.

     lpinum  Sets the lines per inch. For num use 6 or 8.

     The following commands must be sent in the given order and sequence. The sequence looks like,

	   hpset [characterset] [characterdistance] [character density]
	   [point size] [type position] [line strength] [type]

	   -Characterset

		   english	   ISO 4

		   ansi 	   ANSI ASCII ISO 6

		   sweden	   ISO 10

		   italian	   ISO 15

		   spain	   ISO 17

		   german	   ISO 21

		   france	   ISO 69

	   -Characterdistance

		   prop    Proportional

		   fix	   Fixed

	   If you've chosen proportional you don't have to set the character density.

	   -Characterdensity

		   cpi#    # is one of 5,6,10,12,16,16.67,20,24

	   -Pointsize

		   point#  # is one of 4.75,5,6,7,8,9.5,10,12,14,19,24

	   -Typeposition

		   italic
		   upright

	   -Linestrength

		   bold
		   normal

	   -Type
		   courier
		   times
		   gothic
		   univers

	   Notice that not every combination of the commands above is possible. Refer
	   to the manual of HPSET where you can find a table with allowed combinations.

SEE ALSO

     lpr(1), lpd(1),

BUGS

     report them to michael.janson@stud.uni-karlsruhe.de

LINUX
								  April 27, 1997							     LINUX
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