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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 302983598 by alex_5161 on Thursday 13th of October 2016 04:19:09 PM
Old 10-13-2016
Thank you, jim mcnamara, it is perfectly helps!
Sure here is more than I need in my case, but everything is clear and strait forward!
Additionaly, your code keep a way to switch back that not needed right now, but could be a task later on such approach!

Also I've found useful (by another reply) the 'freopen()' C-function and did it in very simple way, too.
(... for anybody else with the same task and for myself later, here is how I did it with freopen() ) :
Code:
#include <iostream>
#include <fstream>
#include <stdio.h>

using namespace std;

void redir(char* fl_nm)
{
  freopen(fl_nm,"a",stdout);
}

int main()
{
   cout << "starting - by cout\n";
   printf(" this written by printf()\n Following messages shoul go to the file '/tmp/tst_redir.log'\n");

   redir((char*)"/tmp/tst_redir.log");

   cout << ".. By 'cout' after using the redir(): this should be written to the file\n";
   printf(" .. By printf() after 'redir()'...\n");

  return 0;
}

But, again, thanks for your solution!!
 

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LEARN ABOUT NETBSD

daemon

DAEMON(3)						   BSD Library Functions Manual 						 DAEMON(3)

NAME

     daemon -- run in the background

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <stdlib.h>

     int
     daemon(int nochdir, int noclose);

DESCRIPTION

     The daemon() function is for programs wishing to detach themselves from the controlling terminal and run in the background as system daemons.

     Unless the argument nochdir is non-zero, daemon() changes the current working directory to the root (/).

     Unless the argument noclose is non-zero, daemon() will redirect standard input, standard output and standard error to /dev/null.

RETURN VALUES

     On return 0 indicates success with -1 indicating error.

ERRORS

     The function daemon() may fail and set errno for any of the errors specified for the library functions fork(2) and setsid(2).

SEE ALSO

     fork(2), setsid(2)

HISTORY

     The daemon() function first appeared in 4.4BSD.

CAVEATS

     Unless the noclose argument is non-zero, daemon() will close the first three file descriptors and redirect them to /dev/null.  Normally,
     these correspond to standard input, standard output and standard error.  However, if any of those file descriptors refer to something else
     they will still be closed, resulting in incorrect behavior of the calling program.  This can happen if any of standard input, standard output
     or standard error have been closed before the program was run.  Programs using daemon() should therefore make sure to either call daemon()
     before opening any files or sockets or, alternately, verifying that any file descriptors obtained have a value greater than 2.

BUGS

     daemon() uses fork() as part of its tty detachment mechanism.  Consequently the process id changes when daemon() is invoked.  Processes
     employing daemon() can not be reliably waited upon until daemon() has been invoked.

BSD
								 September 3, 1999							       BSD
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