When I SSH into a particular server and launch screen, it ignores my CTRL+a key combo. Instead of CTRL+a c creating a new screen window, it instead acts as if I had just typed c. Other key combos fail in a similar way.
I've tried launching screen using screen -e ^jj to bind to j instead of a, but I still get the same result as above.
I tried adding a .screenrc file to my homedir that I know works on other machines, but it has no impact.
I also tried launch a zsh shell instead of bash.
Any ideas where to start to try and fix this? This basically renders screen unusable.
Thanks
screen reads commands from several configuration files during startup, as described in the FILES section of the man page or the Customizing Screen section of the User's Manual (also available, if it's installed, by typing info screen).
The files read are:
The file named by the $SYSSCREENRC environment variable (this may or may not be enabled)
/etc/screenrc
The file named by the $SCREENRC environment variable`
$HOME/.screenrc
(These interact and are searched in various ways that I don't entirely understand.)
In your particular case, based on the comments, the system on which you're running screen happens to have a /etc/screenrc file that contains an escape command that overrides the default.
A digression: in my own $HOME/.screenrc I have:
escape ^#^#
This sets the escape character to the null character, which can be entered by typing Ctrl-space. I find it easier to type, and less likely to conflict with other uses, than the default Ctrl-A. The only conflict I run into is the Emac set-mark-command function, and for that it's easy enough to type it twice.
Related
So I have recently begun using the terminal on my Macbook air and was wondering if anyone could provide an explanation of the first 2 lines that pop up when you open Terminal. They are as follows:
Last login: Sat Feb 20 11:53:48 on ttys000
emilys-iphone-2:~ AidanTakami$
More specifically, who is emily and why is her iPhone shown on my terminal?
You will find no other piece of software on your macbook that allows you to do more than the terminal. It may not seem like it at first, looking at that simple prompt, but the terminal literally gives you the keys-to-the-kingdom.
That said, back to your two lines. The first is a standard login response telling you when and from where your user last logged into that machine (the data is usually read from /var/log/wtmp, see man last).
The second line, your prompt, is controlled by the PS1 shell variable (see man bash (or your shell's manual)). It can be configured to your liking using the various well-documented escape codes and any constant data you include. You can temporarily change the prompt by simply typing PS1=<your wanted string>. A helpful link is Prompt magic - IBM. My favorite is PS1="\[\e[0;37m\]\D{%R}\[\e[1;34m\] \h:\w> \[\e[0m\]", which results in a prompt containing the time , hostname and path information. (in a form that can be cut-and-pasted for shell operations (e.g. cp, mv, ssh, rsync, etc...) :
14:25 alchemy:~/dev/src-c/tmp/refmt>
(note: you can adjust the colors by changing the escape codes to set the color of choice. Also above \D{%R} is the formatted time, \h is the hostname and \w is the path information. The remaining escapes set the colors and \[\e[0m\] terminates a sequence of escape codes (necessary so the proper prompt length can be computed by the shell))
There are a number of shell variables that control how the PS1 prompt behaves, such as PROMPT_DIRTRIM (which controls how many directory levels are shown in the path component if included) This information is available in your shell's manual page. You can also set separate prompts for each user. For example, for root I generally use, PS1="\[\e[1;34m\][\[\e[1;31m\]\A \[\e[1;34m\]\h\[\e[0;31m\]:\w\[\e[1;34m\]] # \[\e[0m\]" which provides immediate visual indication that I am working as root (so you can do what you need, and quickly exit to your normal user again). e.g.:
[14:27 alchemy:.../src-c/tmp/refmt] #
To make your prompt changes permanent, set the desired value in your startup file (like in your ~/.bashrc for your individual user, or in the system startup file for all users)
Hope this has helped.
One of my Emacs keybindings is C-', which works well in GUI. In terminal however, it is not being recognised. I understand that I need to figure out the actual characters sent to the terminal by C-' and map it in the emacs config.
Following the advice of https://unix.stackexchange.com/questions/76566/where-do-i-find-a-list-of-terminal-key-codes-to-remap-shortcuts-in-bash, sed -n l is returning back to me a an empty line, even without the ending $. Does Terminal not recognise the C-' sequence at all?
It depends on your terminal emulator. Emacs-the-GUI essentially is a terminal plus Emacs, so it is reading keystrokes directly from the keyboard (well, via the OS, but you can ignore that detail). As such, it can interpret any keystroke it receives. Your terminal emulator, however, is by default treating Control-' as a plain ', so you'll have to configure it to pass a different character (or character sequence) through to whatever process is running in the current terminal window.
How can I capture the input/ output from a script in realtime (such as with tee), but line-by-line instead of character-by-character? My goal is to capture the input typed into the interactive prompts of a script only after backspaces and auto-completion have finished processing (after the RETURN key is hit).
Specifically, I am trying to create a wrapper script for ssh that creates a timestamped log of commands used on remote servers. The script, which uses tee to redirect the output for filtering, works well, but the redirected output gets jumbled with unsubmitted characters whenever I use the backspace key or the up/down keys to scroll through my remote history. For example: service test stopexitservice test stopart or cd ..logs[1Pls -al.
Perhaps there is a way to capture the terminal's scrollback and redirect that like with tee?
Update: I have found a character-based cleanup solution that does what I want most of the time. However, I am still hoping for an answer to this question (which may well be msw's answer that it is very difficult to do).
In the Unix world there are two primary modes of handling keyboard input. These are known as 'raw' in which characters are passed from the terminal to the reading program one at a time. This is the mode that editors (and such) will use because the editor needs to respond immediately when you press a key.
The other terminal discipline is called 'cooked' which is the line by line behavior that you think of as the bash line by line input where you get to backspace and the command is not executed until you press return. Ssh has to take your input in raw, character-by-character mode because it has no idea what is running on the other side. For example, if you are running an editor on the far side, it can't wait for a return before sending the key-press. So, as some have suggested, grabbing shell history on the far side is the only reasonable way to get a command-by-command record of the bash commands you typed.
I oversimplified for clarity; actually most installations of bash take input in raw mode because they allow editor like command modification. For example, Ctrl-P scrolls up the command history or Ctrl-A goes to the beginning of the line. And bash needs to be able to get those keys the moment they are typed not waiting for a return.
This is another reason that capturing on the local side is obnoxiously difficult: if you capture on the local side, the stream will be filled with Backspaces and all of bash's editing commands. To get a true transcript of what the remote shell actually executed you have to parse the character stream as if you were the remote shell. There also a problem if you run something like
vi /some_file/which_is_on_the_remote/machine
the input stream to the local ssh will be filled with movement commands snippets of text including backspaces and so on and it would be bloody difficult to figure out what is part of a bash command and what is you talking to the editor.
Few things involving computers are impossible; getting clean input from the local side of an ssh invocation is really, really hard.
I question the actual utility of recording the commands that you execute on a local or remote machine. The reason is that there is so much state which is not visible from a command log. As a simple example here's a log of two commands:
17:00$ cp important_file important_file.bak
17:15$ rm important_file
and two days later you are trying to figure out whether important_file.bak should have the contents you intended or not. Given that log you can't answer that simple question. Even if you had the sequence
16:58$ cat important_file
17:00$ cp important_file important_file.bak
17:15$ rm important_file
If you aren't capturing the output, the cat in the log will not tell you anything. Give me almost any command sequence and I can envision a scenario in which it will not give you the information you need to make sense of what was done.
For a very similar purpose I use GNU screen which offer the option to record everything you do in a shell session (INPUT/OUTPUT). The log it creates also comes with undesirable characters but I clean them with perl:
perl -ne 's/\x1b[[()=][;?0-9]*[0-9A-Za-z]?//g;s/\r//g;s/\007//g;print' < screenlog.0
I hope this helps.
Some features of screen:
http://speaking-my-language.blogspot.com/2010/09/top-5-underused-gnu-screen-features.html
Site I found the perl-oneliner:
https://superuser.com/questions/99128/removing-the-escape-characters-from-gnu-screens-screenlog-n
Every now and then when using the ack-vim plugin the font in my window will change to all symbols. I've yet to see any pattern to when this happens. Any suggestions on the cause and possible remedy would be appreciated.
I've seen that happen when binary content got printed to the terminal. Do your Ack queries potentially include binary files?
A fix might be
:!echo -e '\ec\e(K\e[J'
These ANSI Escape sequences attempt to reset the terminal:
# "ESC c" - sends reset to the terminal.
# "ESC ( K" - reloads the screen output mapping table.
# "ESC [ J" - erases display.
This looks like the typical character set translation enabled by the Shift Out control character; you usually just need to send the Shift In control character to counteract it.
Basically, something is outputting a C-n character (Control-N, U+000E, named Shift Out) which tells your terminal to switch to a different display character set. You should be able to get your terminal to switch back to the normal display character set by sending a C-o (Control-O, U+000F, named Shift In) to it.
If you are in Vim, then you can probably send the C-o with a command like this:
:!printf \\017
You will have to type (or paste) this command “blindly” since (due to the alternate character set) you will probably not be able to read what you are typing. If you are typing it (not pasting), then you can also type C-v C-o (to insert a single, literal C-o) instead of the backslashed octal, if that is easier to remember.
If you find that this problem occurs only sporadically when you use the vim-ack plugin, then perhaps some bit of the text results contains the problematic Shift Out character. You might try searching for the file with a command like this:
grep -FRl $(printf \\016) .
Once you know the names of the files, then you should be able to use Vim to search for the character (start a search and type C-v C-n to insert a literal C-n). Maybe it is just some garbage that you can clean out, or maybe you can configure your ack-based searches to exclude the problematic files.
You also tagged the question with tmux. I can not tell for sure, but it looks like the top line might be a tmux status line. Since this line is also corrupted it indicates that it your external terminal emulator that has switched character sets, not just one of your tmux panes.
If you send Shift Out or Shift In directly to a tmux pane it will only affect that pane (each pane is emulated independently), so your status like could not have been munged just by a stray Shift Out hitting a single pane.
If you are running inside tmux, then the easiest way to reset the outside terminal is to suspend and resume your tmux client (or detach from and reattach to your session). tmux pretty much resets the outside terminal when it gives up control.
Depending on the situation, you may also have to reset the character set of the tmux pane by sending it a C-o, too (i.e. printf \\017 at a shell, or a :! prompt in Vim).
It is easy to see how a stray Shift Out could reconfigure a single tmux pane, but it is harder to see how it could have “leaked” out to reconfigure the external terminal (tmux is pretty good at isolating things like this). However, there is a control sequence that tmux recognizes that instructs it to pass data directly to the external terminal (thus “leaking out”), but it is much less likely that you would randomly encounter this sequence since it is much longer:
printf '\ePtmux;%s\e\\' 'stuff bound for the external terminal'
You could use it to send the restorative Shift In like this:
printf '\ePtmux;%s\e\\' $(printf \\017)
You will also want to tell tmux to redraw itself after this (by default, the refresh-client command is bound to C-b r).
It is probably easier to just suspend and resume (or detach and reattach), but this sequence is useful if that is not possible. It also provides a means toward understanding what kind of sequence might “leak” out of tmux to switch the character set of the external terminal.
I'm writing a command interpreter like BASH, and a \ followed by a newline implies a continuation of the input stream; how can I implement that in Win32?
If I use the console mode with ENABLE_LINE_INPUT, then the user can't press backspace in order to go back to the previous line; Windows prevents him from doing so. But if I don't set ENABLE_LINE_INPUT, then I have to manually reposition the cursor, which is rather tedious given that (1) the user might have redirected the input stream, and that (2) it might be prone to race conditions, and I'd rather have Windows do it if I can.
Any way to have my newline and eat it too?
Edit:
If this would require undocumented CSRSS port requests, then I'm still interested!
Assuming you want this to run in a window, like command prompt does by default, rather than full screen, you could create a GUI application with a large textbox. Users would type into the textbox, and you could parse whatever was entered, and output to the same box (effectively emulated the Win32 Console).
This way whatever rules you want to set for how the console behaves is completely up to you.
I might be mistaken is saying this, but I believe that the Win32 Console from XP onward works exactly like this, and it just listens for output on stdout; there shouldn't be any reason you can't do the same.
Hope this was helpful.