I am writing a commandline calculator in C, and it would be very useful if it had the ability to move the cursor each time you close (for example) a parenthesis highlighting the previous one, like in emacs, etc.
For example, if you launch emacs, and type:
(blah)
then for a while after you type the closing parenthesis, the first one is highlighted.
I've tried some googling, but I don't really know what to search for.
Is there a simple and multiplatform (at the very least it's fine if it'd work on Linux, but I'd like it to work at least on Windows as well) way to move the cursor in this way?
If you want better control over the console, take a look at the ncurses library.
The Linux console can also be controlled through console codes. No libraries needed, just printf the appropriate codes to stdout.
The things you should search for are 'termcap', 'terminfo' or 'curses.'
ncurses should be able to do what you're asking for.
Check out ANSI escape codes. They are pretty basic, but a good place to start. The upshot is that they work for most terminals (Linux and Windows).
Related
I'm having a hard time even googling this, because I don't know the right keywords. Some command-line apps (such as vi and less) take over the whole console screen and present an interactive interface to the user. Upon exiting such an app, the screen is returned to the state it was in before the app was launched. I want to write a program that behaves in this fashion, but again, I don't even know what this is called, so I can't find any documentation for how it's accomplished.
So, my question is threefold:
What keywords can I use to find documentation on this?
If you are so inclined, links to such documentation would be helpful.
Lastly, can I accomplish this in a scripting language like Ruby, or even bash? I have no problem with C, but the environment I work in is more amenable to interpreted languages.
As said in some comments, you are looking for ncurses. The Linux Documentation Project have a very good HOWTO on ncurses for C that I used myself to start on it
https://tldp.org/HOWTO/NCURSES-Programming-HOWTO/
The feature you are describing is the alternate screen buffer. I think that [N]Curses will enable this by default. There are certainly curses bindings for Ruby, Python, and other scripting languages.
you can even access ncurses in bash by using the tput program. The whole ncurses library (like curses before it) works by sending escape sequences to the terminal. The xterm program emulates a vt100 terminal (and also a Tektronic terminal) and there were various combinations of characters which would move the cursor, clear the screen, draw various characters etc. These would generally start with an escape character, hence the name: escape sequence. You also sometimes see these escape sequences in people's PS1 shell variables with the \e to provide the escape character; often used to colour the prompt or set the window title.
tput refers to the terminfo database to figure out what the escape sequences are to perform the functions you've asked it to do.
see the manual page, type:
man 5 terminfo
for more details
Pre-Note: By portable here, I mean cross-terminal, not cross-os or cross-platform. Different terminals support different codes for different colors (why btw?)
So, I want cool PORTABLE terminal colors. Searching around google, you find the same old options, but I don't want those. I want TERMINAL output. Like running apt produces brownish text sometimes, I don't want a window in ncurses, nor do I want to hardcode ANSI escape codes like \033[31m. Those are the two traditional options I do NOT WANT.
What I want is like this:
$ some program that doesn't really matter
blah blah earlier terminal output
$ colortest
Hello, World, but this part of the text would be in blue or something!
No window that erases my earlier terminal output or uses alternate screen buffer or anything. I want to do in C what I can do in bash with tput setaf and printf. But I can't find anything. There seems to be no library to do this. The only options I can find are "Use ncurses", which forces the window (as far as I know, I searched around for windowless ncurses but only got the windows download for ncurses), or "Hardcode ANSI codes", which also won't work. Is there any library to do this, or will I need to
write something myself , querying things like terminfo or god forbid termcap? I haven't found this question being asked around earlier, forgive me if it has, but I am tires of the two unsatisfactory workarounds. My only option so far has been calling tput trough popen and such.
I am implementing a shell-like program where user types command (defined by me). Just like this.
>cmd
result blah blah blah
>
When I use arrow keys it outputs raw characters like ^[[A.
>^[[A
I also notice sqlite3 behaves like this at least in the version I compiled on my computer.
How to prevent this and let <- and -> keys move cursor left and right?
GNU Readline is a library specifically designed for this task (that is, allowing the user to edit commands typed at an interactive command-driven program). Note that this library is distributed under the GPL (not the LGPL); if that won't work for you, editline is a similar library with a BSD-style license.
I note that you say this is homework, so you might want to ask your instructor whether you are expected to implement cursor motion and line editing yourself. If so, ncurses (as mentioned by jDourlens) is the next step down in terms of abstraction, and if you really want to do everything yourself, read up on termios and the VT-220 control sequences (nearly all terminal emulators used nowadays emulate the VT220 or one of its descendants).
I have found a slightly simpler way to do that. Run rlwrap [your program] instead of [your program].
For example, it works fine with sqlite3 as rlwrap sqlite3
To let the user navigate in cmd with the keyboards arrows you may have to use termcaps.
http://www.gnu.org/software/termutils/manual/termcap-1.3/html_chapter/termcap_2.html
If you want to be easier to deal with termcaps that are a bit complex you shoul use Ncurses.
http://www.gnu.org/software/ncurses/ncurses.html
Good luck to deal with termcaps if you chosse this solution, it's some pain in the ass!
You may take a look to Ncurses. It's a library that let you control almost everything in terminals. The specific function you want is noecho(), which stops terminals from showing users' input.
I can't seem to find the right way to ask the almighty google...
In such programs as a command-line progress bar, the output buffer seems to be directly manipulated. It can't print a character to a terminal in any place it wants. How is such control over a program's output controlled in standard C? Is there a special library that I can look up?
look at curses
it`s a lib for unix/linux
If you just want a progress bar, you can just print a single 'X' for every 2% completion. This should fill 50 characters on a line.
If you want something more fancy, on Linux you can try the classic "curses" library, or if you just want a dialog box, you could try the library that the Debian install utilities use, but I forget its name.
you can do the progress bar with \r check this
for doing more advanced stuff you can use ncurses
It's not part of standard C. These things work by writing some special character sequences that are recognized by the terminal emulator which takes care of the cursor positioning and stuff.
The big gorilla here is the ncurses library, but you can do a lot of cool stuff with less learning curve. Try using \r to move to beginning of line and using simple control sequences to clear to end of line, turn bold on and off, etcetera. The tput(1) command is invaluable. For example, I wrote a simple application the does highlighted text, and to turn highlighting on and off I just called the commands tput smso and tput rmso. You can capture the results using C with popen(3); using a shell it is even easier.
You could use ANSI escape coding to control the termincal output. This is how a lot of MUD games do their output.
I am writing a program that's similar to a shell. Once started up, there's a prompt and you enter in some app-specific commands.
So far this works just fine. However, I want to add support for command history like in Bash, so the user could hit the up or down arrow and see previously entered commands.
I have included the ncurses library, and I have done a simple hello world test with getch() to make sure the up and down arrows are reported correctly.
The thing that's bothering me is that it seems to be a requirement that I call initscr() which will clear the screen in order for me to use getch().
OKAY SO THE QUESTION IS:
Does anybody know a way to use ncurses getch() function without calling initscr() first? If not, can I make it not clear the screen? Basically, I'm looking to have getch() act the same as getchar(), if that makes sense.
Thanks in advance!
EDIT: I think the best example of this is how Python runs in interactive mode.
Curses wants to fully control the screen, and to optimize writes to the screen, especially over slow serial lines. To do this, it needs to know what is on the screen, and the only reasonable way to do that with most terminals is to start from an empty screen and keep track of what you write to the terminal.
Thus, I suspect (n)curses is the wrong tool for your shell. You probably need to go down a step on the abstraction layer and use terminfo and non-blocking reads from the terminal (standard input) instead.
(This is not very helpful. Sorry.)
It might be simpler to use an interface like readline() rather than resorting to full-blown ncurses.
You could just call your program from within rlwrap and have the functionality without the pain...
Here is another discussion about this. The provided solutions are:
"The 'filter()' function lets you use curses as a single-line."
"You can write something equivalent in C, using setupterm to get the
terminal data, and tparm, tputs for formatting and output."
Of course there is the third option to get the ncurses source code and modify it so it doesn't clear the screen anymore.
Have you considered the simple expedient of creating a custom terminfo or termcap entry lacking a sequence to clear the screen and then switching your terminal setting to that right before running your program? You could also just use newterm() and set_term() in ncurses. This used to be easier with termcap, since you could include another terminal and override some of its capabilities.