I find it hard to explain but I will try my best. Some times in Linux- in the Terminal- things get printed but you can still write over them. eg when using wget you get a progress bar like this:
[===================> ]
Now if you type something while it is doing this it will 'overwrite' it. My question is how to recreate this in c++.
Will you use something like
cout <<
or something else?
I hope you understand what I am getting at...
btw I am using the most recent version of Arch with xfce4
Printing a carriage return character \r is typically interpreted in Linux as returning you to the beginning of the line. Try this, for example:
std::cout << "Hello\rJ";
The output will be:
Jello
This does depend on your terminal, however, so you should look up the meaning of particular control characters for your terminal.
For a more cross-platform solution and the ability to do more complex text-based user interfaces, take a look at ncurses.
You can print the special character \b to go back one space. Then you can print a space to blank it out, or another character to overwrite what was there. You can also use \r to return to the beginning of the current output line and write again from there.
Controlling the terminal involved sending various escape sequences to it, in order to move the cursor around and such.
http://www.ibiblio.org/pub/historic-linux/ftp-archives/tsx-11.mit.edu/Oct-07-1996/info/vt102.codes
You could also use ncurses to do this.
Related
As the title says, I am wondering how to delete a newline that is printed to the console, if it is possible.
I have seen the following:
How to delete a newline using \b
Except that is about using \b to delete a new line, and I would just like to know how to do it, using any possible method.
More specifically:
If I have
----
- -
----
printed to the console, I would like to know how to delete the last two lines, to have just ----.
Thanks in advance!
Note: I left out an OS to see if I can get an answer that would work on any OS.
As I know, there is no portable way to work with not only current line of output,
but with several lines on console.
So you need some kind of wrapper around suitable functionality in each OS,
the most portable library for this, as I know is:
http://pdcurses.sourceforge.net/
How can I remap alt+backspace to delete words like native *NIX text manipulation? I checked out this thread: Using alt+backspace key in vim command line to delete by words
And the examples like: cmap <a-bs> <c-w> and :imap <A-BS> <C-W> don't do anything. And the accepted answer was actually to not even remap it, but to use ctrl+w. Since VIM's alt+backspace doesn't do anything I'd rather remap it to something I'm used to.
I'm using terminal based VIM (specifically in iTerm)
On macOS with iTerm2, I have the option keys mapped to +Esc (like many people), and I found that pressing Option+Backspace actually was interpreted by vim as an Escape press followed by a Backspace press, so the following binding worked perfectly for me; I recommend trying it even if your configuration is different than mine, just in case it works for you!
:imap <Esc><BS> <C-w>
The Alt/Meta key is problematic in Vim and most terminals, see this answer of mine for an overview of the situation (the situation is the same for Meta and Alt).
In short, Vim doesn't receive Alt at all: hitting Alt+Backspace is exactly the same as hitting Backspace.
Anyway, it will be better for you in the long term to learn and get accustomed to Vim's default key-mappings.
If you are on OSX, macvim uses the standard key bindings, so pressing Alt+Backspace will delete the entire word. Same goes for navigating between words with Alt+RightArrow and Alt+LeftArrow.
I want to create a C++ console application that print some text to different parts of the console. For example in QBasic you can use:
locate(8,5)
print "hi"
And hi would be printed in column 8 line 5. In C++ when I use cout it always prints on the next line, and begins printing in the first column.
Is there any way I can do this?
C++ itself does not have this feature, it's I/O model is a fairly simple, sequential one.
If you want to do fancy cursor positioning, you'll need to output (for example) control characters which your terminal will recognise as special commands (such as ANSI or VT escape sequences), or use a library like curses (see ncurses here) which can do a lot of the grunt work for you, not just cursor positioning but also things like text mode windows and so forth.
A library, like ncurses can help you do this.
Okay, I have been researching on how to do this, but say I am running a program that has a whole bit of output on the terminal, how would I clear the screen from within my program so that I can keep my program running?
I know I can just type clear in terminal and it clears it fine, but like I said, for this program it would be more beneficial for me.
I found something that works, however, I'm not sure what it is or what it is doing.
cout << "\033[2J\033[1;1H";
That works but I have no clue what it is, if you could explain it, than I would much appreciate it.
These are ANSI escape codes. The first one (\033[2J) clears the entire screen (J) from top to bottom (2). The second code (\033[1;1H) positions the cursor at row 1, column 1.
All ANSI escapes begin with the sequence ESC[, have zero or more parameters delimited by ;, and end with a command letter (J and H in your case). \033 is the C-style octal sequence for the escape character.
See here for the full roadshow.
Instead of depending on specific escape sequences that may break in unexpected situations (though accepting that trade-off is fine, if it's what you want), you can just do the same thing you'd do at your shell:
std::system("clear");
Though generally system() is to be avoided, for a user-interactive program neither the extra shell parsing nor process overhead is significant. There's no problem with shell escaping either, in this case.
You could always fork/exec to call clear if you did want to avoid system(). If you're already using [n]curses or another terminal library, use that.
For portability you should get the string from termcap's cl (clear) capability (Clear screen and cursor home). (Or use std::system("clear") as told by Roger Pate).
man 3 termcap (in ncurses)
man 5 termcap
set | grep TERMCAP
you can write in a terminal "clear > data" and read in data the escapes sequance
0x1B[H0x1B[2J0x1B[3J
so
std::cout << "\033[H\033[2J\033[3J" ;
What's the vi/gvim syntax to replace a pattern with a pattern that includes <ENTER>? I know this is possible but never felt like diving too deep in the documentation to know how to do it.
Something like this:
:s/\(word\)/\1<ENTER>/
But correctly :)
Thanks
Use the "escape" encoding:
:s/\(word\)/\1\r/
See the Vim documentation for pattern whitespace escapes.
:s/\(word\)/\1\r/
Alternatively, use Ctrl+V or Ctrl+Q to quote (escape) the Enter key:
:s/\(word\)\1^QENTER/
Where ^Q is Ctrl+Q and ENTER is the Enter key.
Clarification: Depending on your installation, either ^Q or ^V should work. The quoting character differs on some platforms.
(This has the helpful side-effect of inserting the appropriate end-of-line character for whichever platform you're using, eliminating the CR vs. LF vs. CRLF problem.)
Just for clarification purposes, now that we're talking about carriage return, it should be noted that RETURN and ENTER key are not the same, or it would be more correct to say, they should not be the same.
I haven't used a desktop keyboard for some time now, but the ENTER key is usually the one on the down right side, while the RETURN key is the big one in the middle.
RETURN key is the one that should be used for entering a carriage return, while ENTER key is the one that should be used for entering commands. I remember an old DOS editor EDT, in which RETURN key was for newline and ENTER key was for giving commands. You couldn't give a command with RETURN. I think ENTER also gave ^1 (line feed).
Today that difference is somewhat lost, although I still, now and then, run into an editor that respects it.
2 examples:
One, two and an even more obvious three