int len = strlen( key );
char *buf;
buf = malloc( len+1 );
memset( buf, 0, len+1 );
fread( buf, 1, len, fp );
while(1){
　if( !strcmp( key, buf ) ){
　　puts( "agree" );
　}
　memmove( buf, buf+1, len-1 );
　if( !fread( buf+len-1, 1, 1, fp ) ){
　　break;
　}
}
free(buf);