:redir >name_of_registers_file :registers :redir END :r name_of_registers_file :help redir The last command is very useful, since there are lots of options for redirection: to variables, to registers, how to append, further cornucopia. I still find it weird and annoying that it uses END that way, but since everything else that can follow redir has to … Read more
There is a command line option for logging. The output is saved to screenlog.n file, where n is a number of the screen. From man pages of screen: ‘-L’ Tell screen to turn on automatic output logging for the windows.
Portably, you can get the next character in the input stream with getchar() and then push it back with ungetc(), which results in a state as if the character wasn’t removed from the stream. The ungetc function pushes the character specified by c (converted to an unsigned char) back onto the input stream pointed to … Read more
The answers to these questions vary depending on whether you are using a stream socket (SOCK_STREAM) or a datagram socket (SOCK_DGRAM) – within TCP/IP, the former corresponds to TCP and the latter to UDP. How do you know how big to make the buffer passed to recv()? SOCK_STREAM: It doesn’t really matter too much. If … Read more
This is basically due to function call overhead and indirection. The ofstream::write() method is inherited from ostream. That function is not inlined in libstdc++, which is the first source of overhead. Then ostream::write() has to call rdbuf()->sputn() to do the actual writing, which is a virtual function call. On top of that, libstdc++ redirects sputn() … Read more
This is not how you initialize an array, but for: The first declaration: char buf[10] = “”; is equivalent to char buf[10] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; The second declaration: char buf[10] = ” “; is equivalent to char buf[10] = {‘ ‘, 0, 0, 0, 0, 0, 0, … Read more
Consider writing to a file. This is an expensive operation. If in your code you write one byte at a time, then each write of a byte is going to be very costly. So a common way to improve performance is to store the data that you are writing in a temporary buffer. Only when … Read more
There is no strict rule by the standard – only that endl WILL flush, but the implementation may flush at any time it “likes”. And of course, the sum of all digits in under 400K is 6 * 400K = 2.4MB, and that’s very unlikely to fit in the buffer, and the loop is fast … Read more
For file streams, you can use pubsetbuf for that : std::ifstream f; f.rdbuf()->pubsetbuf(0, 0); f.open(“test”); Explanation The C++ standard says the following about the effect of setbuf (and thus pubsetbuf) for file streams : If setbuf(0,0) is called on a stream before any I/O has occurred on that stream, the stream becomes unbuffered. Otherwise the … Read more
When shutting down the LogManager: LogManager.shutdown(); all buffered logs get flushed.