#include <stdio.h>#ifdef unix#include <unistd.h>#endif#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#ifndef O_BINARY#define O_BINARY 0#endif#define NB 8192char buff[NB];intmain(argc,argv)int argc;char **argv;{int fdi, fdo, i, n, m;char *p, *q;char c;if( argc > 0 )	printf( "%s:  Reverse bytes in 8-byte values \n", argv[0] );if( argc > 1 )	strcpy( buff, argv[1] );else	{	printf( "Input file name ? " );	gets( buff );	}fdi = open( buff, O_BINARY | O_RDONLY, S_IREAD );if( fdi <= 0 )	{	printf( "Can't open <%s>\n", buff );	exit(2);	}if( argc > 2 )	strcpy( buff, argv[2] );else	{	printf( "Output file name ? " );	gets( buff );	}fdo = open( buff, O_BINARY | O_RDWR | O_CREAT | O_TRUNC,      S_IREAD | S_IWRITE );if( fdo <= 0 )	{	printf( "Can't open <%s>\n", buff );	exit(2);	}while( (n = read( fdi, buff, NB )) > 0 )	{	m = n / 8;	p = buff;	q = buff+7;	for( i=0; i<m; i++ )		{		c = *p;		*p++ = *q;		*q-- = c;		c = *p;		*p++ = *q;		*q-- = c;		c = *p;		*p++ = *q;		*q-- = c;		c = *p;		*p++ = *q;		*q-- = c;		p += 4;		q += 12;		}	write( fdo, buff, n );	}close( fdo );close( fdi );exit(0);}