...低水準入出力関数おぼえたて

#include <いろいろ>
unsigned char buffer[ 1024 ];
int fdi, fdo;
void writesub ( char * );
int main( int argc, char *argv[] ){
if ( argc != 4 ){
fprintf( stderr, "usage %s input1 input2 output\n", argv[ 0 ] );
exit( EXIT_FAILURE );
}
if ( ( fdo = open( argv[ 3 ], O_WRONLY|O_TRUNC ) ) < 0 )
fdo = creat( argv[ 3 ], S_IREAD|S_IWRITE );
writesub( argv[ 1 ] );
lseek( fdo, 0, SEEK_END );
writesub( argv[ 2 ] );
close( fdo );
return EXIT_SUCCESS;
}
void writesub( char *arg ){
int flg;
fdi = open( arg, O_RDONLY );
while ( 1 ){
if ( ( flg = read( fdi, buffer, 1024 ) ) > 0 )
write( fdo, buffer, flg );
else if ( flg == 0 ) break;
else puts( "NEVERMIND" );
}
close( fdi );
}