/*********************************************************
 *
 * redirect.c
 *
 * 4/16/02 Jeff Ondich
 *
 * This program illustrates the use of the dup2 function
 * to redirect the standard input and standard output.
 * Compile and run it in a directory that contains a
 * file named moose.txt.  It will send its output to
 * a file named elk.txt.
 *
 * Note that I do not check the return value of close(),
 * since this is a very small program which won't change
 * its behavior even if the file closing fails, and since
 * all the files will get closed when the program terminates,
 * anyway.
 * 
 *********************************************************/

#include    <stdio.h>
#include    <stdlib.h>
#include    <unistd.h>
#include    <sys/types.h>
#include    <sys/stat.h>
#include    <fcntl.h>
#include    <ctype.h>

int main()
{
    char    ch;
    int        inputFD, outputFD;
    
    
    /* Open the input file for reading. */

    inputFD = open( "moose.txt", O_RDONLY );
    if( inputFD == -1 )
    {
        perror( "Trouble opening moose.txt" );
        exit( 1 );
    }


    /* Attach the opened moose.txt to standard input. */

    if( dup2( inputFD, STDIN_FILENO ) == -1 )
    {
        perror( "Trouble with dup2 to stdin" );
        close( inputFD );
        exit( 1 );
    }


    /* Close the inputFD file descriptor.  Note that this
       leaves the duplicated file descriptor stdin open. */

    close( inputFD );


    /* Play the same open/dup2/close game with stdout. */

    outputFD = open( "elk.txt", O_RDWR | O_CREAT, 0644 );
    if( outputFD == -1 )
    {
        perror( "Trouble opening elk.txt" );
        exit( 1 );
    }

    if( dup2( outputFD, STDOUT_FILENO ) == -1 )
    {
        perror( "Trouble with dup2 to stdout" );
        close( outputFD );
        exit( 1 );
    }

    close( outputFD );


    /* Finally, read the contents of moose.txt via
        stdin and send them in uppercase form to
        elk.txt via stdout. */

    while( (ch=getchar()) != EOF )
    {
        putchar( toupper( ch ) );
    }


    return 0;
}