The R interactive interface implements the shell-like read line behavior (I have no better words to formulate this...).
For example, pressing Ctrl-W kills the preceding word.
Now, I would like this mechanism to stop at characters other than alphanumeric. For example, if I have entered
data.frame(Ant
and press Ctrl-W, the whole string data.frame(Ant is killed. I would much prefer the Ctrl-W to kill the Ant and stop short of the left parenthesis.
Is there a way of tweaking this behavior?
The behaviour of readline depends upon the operating system and the IDE. On Windows, CRTL-W doesn't delete the previous word. I don't think that there's a trivial way of changing the behaviour. At a guess, start digging around in:
http://svn.r-project.org/R/trunk/src/library/utils/src/io.c
Related
I'm a happy user of the Nvim-R plugin, but I cannot find out how to scroll up in the buffer window that the plugin opens with R. Say for instance that I have a large output in console, but I cannot see the top of it - how do I scroll up to see this? In tmux for instance there's a copy mode that quite handily lets you do this, but how is this done in the R buffer?
An example below where I'm very curious to see what's on the line above the one begining with "is.na(a)...". How can this be achieved?
I have scoured the documentation found here, but without luck.
The answer is apparently to use Ctrl+\ Ctrl+n according to this answer on the bugreports for NVim-R.
Here's what my output looks like when I output mtcars:
When I hit Ctrl+\ Ctrl+n, I can move the cursor and I get line numbers:
To get back to interactive, I just use i, the same way I normally would.
Apparently, if you are using neovim, then you can add let R_esc_term = 0 in your ~/.vimrc file and you can then use the escape key, but if you don't use neovim, you are stuck using the two ctrl commands ¯\_(ツ)_/¯.
As pointed out by ZNK, it is about switching to normal mode in Vim's terminal. This, however, can easily fail due to cumbersome keybinding. If such is the case, remap the default keybinding to something reasonable, say, by putting this in your .vimrc:
tnoremap jk <C-\><C-n>
This works for me in Linux running Vim 8.0 in terminal (e.g. does not require Neovim). As you can see, I use 'jk' to switch from insert to normal mode. One can use Esc instead of jk, however, this makes me unable to use up arrow to retrieve command line history as been reported elsewhere.
I recently installed Zsh in hope of a better life and brighter mornings. However, I quickly realized Zsh introduces various issues in conjunction with tmux.
The first issue was some weird stuff happening at the end of the prompt, before my commands, but this was resolved by supplying tmux with the -u flag for unicode-support. However, I am stuck with one final issue that needs resolution before I can use Zsh with tmux:
Usecase: Autocomplete a command which contains multiple suggestions
Issue: Autocompletion shifts suggestion one character to the right, while leaving the original character behind (visual bug, it is not included in the command)
Example 1.
Then I hit TAB..
Example 2.
Then I hit TAB..
Note 1: This does NOT occur when using the Bash-shell.
Note 2: I am using "oh-my-zsh". This issue only occurs when using the provided themes. This narrows it down to an "oh-my-zsh"-theme issue, not native zsh/tmux.
In case some people still get a similar issue, see also the top-voted answer of Remnant characters when tab completing with ZSH. The plugin you were using may have had the same non-printable characters issue, that would explain the symptoms.
I've seen both:
#!/path/...
#! /path/...
What's right? Does it matter? Is there a history?
I've heard that an ancient version of Unix required there not be a space. But then I heard that was just a rumor. Does anyone know for certain?
Edit: I couldn't think where better to ask this. It is programming related, since the space could make the program operate in a different way, for all I know. Thus I asked it here.
I also have a vague memory that whitespace was not allowed in some old Unix-like systems, but a bit of research doesn't support that.
According to this Wikipedia article, the #! syntax was introduced in Version 8 Unix in January, 1980. Dennis Ritchie's initial announcement of this feature says:
The system has been changed so that if a file being executed begins
with the magic characters #!, the rest of the line is understood to
be the name of an interpreter for the executed file. Previously (and
in fact still) the shell did much of this job; it automatically
executed itself on a text file with executable mode when the text
file's name was typed as a command. Putting the facility into the
system gives the following benefits.
[SNIP]
To take advantage of this wonderful opportunity, put
#! /bin/sh
at the left margin of the first line of your shell scripts. Blanks
after ! are OK. Use a complete pathname (no search is done). At the
moment the whole line is restricted to 16 characters but this limit
will be raised.
It's conceivable that some later Unix-like system supported the #! syntax but didn't allow blanks after the !, but given that the very first implementation explicitly allowed blanks, that seems unlikely.
leonbloy's answer provides some more context.
UPDATE :
The Perl interpreter itself recognizes a line starting with #!, even on systems where that's not recognized by the kernel. Run perldoc perlrun or see this web page for details.
The #! line is always examined for switches as the line is being
parsed. Thus, if you're on a machine that allows only one argument
with the #! line, or worse, doesn't even recognize the #! line, you
still can get consistent switch behaviour regardless of how Perl was
invoked, even if -x was used to find the beginning of the program.
Perl also permits whitespace after the #!.
(Personally, I prefer to write the #! line without whitespace, but it will work either way.)
And leonjoy's answer points to this web page by Sven Mascheck, which discusses the history of #! in depth. (I mention this now because of a recent discussion on comp.unix.shell.)
It seems to usually work both ways. See here. I'd say that the no-space version is much more common today, and, to me, much more appealing.
BTW, this is not specifically related to Perl (but it's definitely related to programming).
I have Vim 7.2 installed on Windows. In GVim, the <C-PageUp> and <C-PageDown> work for navigation between tabs by default. However, it doesn't work for Vim.
I have even added the below lines in _vimrc, but it still does not work.
map <C-PageUp> :tabp<CR>
map <C-PageDown> :tabn<CR>
But, map and works.
map <C-left> :tabp<CR>
map <C-right> :tabn<CR>
Does anybody have a clue why?
The problem you describe is generally caused by vim's terminal settings not knowing the correct character sequence for a given key (on a console, all keystrokes are turned into a sequence of characters). It can also be caused by your console not sending a distinct character sequence for the key you're trying to press.
If it's the former problem, doing something like this can work around it:
:map <CTRL-V><CTRL-PAGEUP> :tabp<CR>
Where <CTRL-V> and <CTRL-PAGEUP> are literally those keys, not "less than, C, T, R, ... etc.".
If it's the latter problem then you need to either adjust the settings of your terminal program or get a different terminal program. (I'm not sure which of these options actually exist on Windows.)
This may seem obvious to many, but konsole users should be aware that some versions bind ctrl-pageup / ctrl-pagedown as secondary bindings to it's own tabbed window feature, (which may not be obvious if you don't use that feature).
Simply clearing them from the 'Configure Shortcuts' menu got them working in vim correctly for me. I guess other terminals may have similar features enabeld by default.
I'm adding this answer, taking details from vi & Vim, to integrate those that are already been given/accepted with some more details that sound very important to me.
The alredy proposed answers
It is true what the other answer says:
map <C-PageUp> :echo "hello"<CR> won't work because Vim doesn't know what escape sequence corresponds to the keycode <C-PageUp>;
one solution is to type the escape sequence explicitly: map ^[[5^ :echo "hello"<CR>, where the escape sequence ^[[5^ (which is in general different from terminal to terminal) can be obtained by Ctrl+VCtrl+PageUp.
One additional important detail
On the other hand the best solution for me is the following
set <F13>=^[[5^
map <F13> :echo "hello"<CR>
which makes use of one of additional function key codes (you can use up to <F37>). Likewise, you could have a bunch of set keycode=escapesequence all together in a single place in your .vimrc (or in another dedicated file that you source from your .vimrc, why not?).
I see console apps print colors and seen apps such as ffmpeg print text over itself instead of a new line. How do I print over an existing line? I want to display fps in my console app either at the very top or very bottom and have regular printfs go there and scroll normally.
I need this for windows, but this is meant to be cross platform, so I will eventually have a linux and mac implementation.
There is two simple possibilities which work on linux as well as windows, but only for one line:
printf("\b"); will return for one character, so you might count how many character you want to backspace and fire this in a loop, or you know that you only write n numbers and do it likeprintf("\b\b\b\b\b\b\b\b\b\b");
printf("text to be overwritten by next printf\r"); this will return the cursor to the beginning of the line, so any next printf will overwrite it. Make sure to write a string of same length or longer so you overwrite it entirely.
If you want to rewrite several lines, there is nothing so portable as ncurses, there is libs for it on practically every operating system, and you don't have to take care of the ANSI-differences.
edit: added link to ncurses wikipedia page, gives great overview and introduction, as well as link list and maybe a translation to your preferred language
Check out ncurses. It has bindings for most scripting languages.
You can use '\r' instead of '\n'.
The ASCII character number 8 (A.K.A. Ctrl-H, BS or Backspace) lets you back up one character. ASCII Character number 13 (A.K.A Ctrl-M, CR or Carriage Return) returns the cursor at the beggining of the line.
If you are working in C try putchar(8); and putchar(13);
The magic of the colors, cursor locating and bliking and so on are inside ANSI escape codes. Any text console capable of handling ANSI codes can use them just printing them out to console (i.e. by means of echo in a bash script or printf() function in C).
Unix terminals support ANSI escape sequences and Windows world used to support them back in old MS-DOS days, but the multibyte console support put an end to this. There is more information here. However there are other ways out of just ANSI sequences printing available on Windows. Moreover if you have Cygwin installed on your Windows maching ANSI codes work just as great as on any Unix terminal.
Many people mention Ncurses library that is the de-facto standard for any gui-like text based applications. What this library does is to hide all the terminal differences (Windows/Unix flavours) to represent the same information as identical as possible across all the platforms, though from my own experience I tell you this is not always true (i.e. typical text window frames change because the especial chars are not available under all character encodings). The counterpart of using ncurses is that it is a complete API and it is much harder to start out with it than simply writing out some ANSI escape sequences for simple things such as change the font color, cleaning screen or moving back the cursor to a random position.
For the sake of completeness I paste an example of use of ANSI sequence under Linux that changes the prompt to blue and shows the date:
PS1="\[\033[34m\][\$(date +%H%M)][\u#\h:\w]$ "
You can use Ncurses -
ncurses package is a subroutine library for terminal-independent screen-painting and input-event handling which presents a high level screen model to the programmer, hiding differences between terminal types and doing automatic optimization of output to change one screenfull of text into another
Depending on the platform which you are developing on there's probably a more powerful API which you could use, rather than old ASCII control codes.
e.g. If you are working on Win32 you can actually manipulate the console screen buffer directly.
A good place to start might be here
http://msdn.microsoft.com/en-us/library/ms683171(VS.85).aspx
I have been looking for similar functions/API which would allow me to access the console as something other than a stream of text for other platforms. Haven't found anything yet, but then again, I haven't been looking that hard.
Hope it helps.