How to give back hand to screen

[sylvain_nurun]

Hello everybody,

I have a little problem..

A program I'm modifying has the following behavior :

If an option is given, it will write information messages to the screen, but if an other option is given, it will write information messages to a File named LogFile.txt ...

Now, what's done in the code is this :

freopen("LogFile.txt", "a+", stdout);
To close stdout and assign LogFile.txt to the standard output.

After everything is done, I need to give back the hand to the screen to write a message about the success of the program, based on some text in an other file.

Everything I saw about the freopen function didn't talk about giving back the hand to the screen..

I use
freopen("NUL", "a+", stdout);
to close the stream stdout assigned to LogFile ( it is shared by a lot of programs called from the main one) , but I can't write anything on the screen from then on.

Does anybody know how I can write back to the screen without leaving the program ?

Thanks
Sylvain

[Devine]

Hi I have been looking for this one for a while, the doc for freopen doesn't mention any of it however it can be found under _dup2 documentation.

Anyway here's the code from it:

/* DUP.C: This program uses the variable old to save
* the original stdout. It then opens a new file named
* new and forces stdout to refer to it. Finally, it
* restores stdout to its original state.
*/

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

void main( void )
{
int old;
FILE *new;

old = _dup( 1 ); /* "old" now refers to "stdout" */
/* Note: file handle 1 == "stdout" */
if( old == -1 )
{
perror( "_dup( 1 ) failure" );
exit( 1 );
}
write( old, "This goes to stdout first\r\n", 27 );
if( ( new = fopen( "data", "w" ) ) == NULL )
{
puts( "Can't open file 'data'\n" );
exit( 1 );
}

/* stdout now refers to file "data" */
if( -1 == _dup2( _fileno( new ), 1 ) )
{
perror( "Can't _dup2 stdout" );
exit( 1 );
}
puts( "This goes to file 'data'\r\n" );

/* Flush stdout stream buffer so it goes to correct file */
fflush( stdout );
fclose( new );

/* Restore original stdout */
_dup2( old, 1 );
puts( "This goes to stdout\n" );
puts( "The file 'data' contains:" );
system( "type data" );
}


Output

This goes to stdout first
This goes to file 'data'

This goes to stdout

The file 'data' contains:

This goes to file 'data'