I have been using the SoX play command line tool to playback audio files from the console, and have noticed that there is a nice little display of the time info and left/right levels that update in real time with the audio source . . .
Screenshot from SoX homepage
However, after cloning the source, I could not find any mention of Ncurses. Does anyone know how SoX achieves this neat little console trick? I just don't know what to look for, or which file to look in to see how this is implemented.
I doubt it's merely using the \b character. My guess would be that it's using the terminal cursor movement commands, which are a set of escape sequences supported by many (but not all) Linux terminals.
You can even use these straight from the command line using echo. For instance:
$ s=($(stty size)); echo -en "\e[2J\e[$((s[0]/2));$((s[1]/2-6))HHello world.\e[${s[0]};0H"
This should give you a blank screen, except for the the message "Hello world." printed right in the middle of the screen, and a prompt at the very bottom.
Related
Is it possible to turn on logging feature by default in xterm?
Lets say for example, I have example program in c that give an output in xterm everytime i ran the program from default bash terminal in linux. And I want to save the output that shows in xterm into a file everytime the programs is run.
I'm using centos7_x86_64 fyi
Thanks.
In Windowmaker:
Hold down ctrl + left click in xterm window (on the terminal text), click on "log to file".
A cool thing to do is when you're coding, log the terminal, and then when you cat the Xterm log, you see coding in fast forward. If you wanted you could video it.
Note that there are also other menus in xterm, accessible using Ctrl+Left Click, Ctrl+Middle Click, Ctrl+Right Click.
Log file will be in the directory that you launched Xterm from, and will be in the format: Xterm.log.<hostname>.<date>.<time>.log.
This is a very good question, there's no reason to mark down a question like this.
It can be done in two ways:
Using script:
xterm -e script mylogfile -c "someCommand -i input_file -o output_file -f someArg"
Redirect to a file:
xterm -e 'someCommand --arguments 2>&1> /path/to/mylogfile'
I do essentially this with "terminal-window", mrxvt, "hcm" and "pypty".
terminal-window wraps mrxvt, just filling in some commandline options. mrxvt is a lightweight, multitabbed, nonunicode terminal emulator not dissimilar to xterm.
hcm is a GUI that makes it easy to run a shell (or other command) on a remote host. It can also start an mrxvt with remote ssh's without requiring the GUI if you prefer (using hcm-term).
pypty is a /usr/bin/script reimplementation that is written in Python. It is not significantly different from /usr/bin/script, except it gives a "dated files mode", that allows you to have one file per pseudo terminal per day. So if you leave a shell logged in overnight, you get one file per day - this tends to make it easier to find what you're looking for.
All this combines to give you pseudo terminal logging with great ease. Commands are run on remote hosts, but logged locally. Just start a "fancy terminal-window" (or use hcm-term), and everything you see on the screen plus control characters (but not nonechoed passwords) will be logged under ~/.hcm/logs/<year>/<month>/<day>/* .
Also, if you hit the shell button in the lower right of mrxvt, you get another ssh session into the same remote host, which is also logged locally (to a different file under ~/.hcm/logs/...). When I started making use of that feature, I had no idea how much I would grow to like it.
You can obtain them from http://stromberg.dnsalias.org/~strombrg/hcm/ There's a video there that shows how easy it is to set up and get started with.
BTW, fancy terminal-window sets up $PS0 or "trap DEBUG" to give you command start times and finish times. It's great for post mortems. It does this without replacing any of the usual bash startup files.
I wrote terminal-window, hcm and pypty, but I can't take credit for mrxvt. :)
HTH
I'm writing a C program that requires to hide the characters a user types from the screen during the program execution. For example, when running the following loop
while (1)
{
//do some work
}
the console displays the blinking cursor (that's good). BUT, when the user types keys on the keyboard, these keys are being echoed out to the console. To visualize it better:
Step 1: Starting the program
root#debian:/home/root# ./program
_
Step 2: User types some characters (even though he shouldn't)
root#debian:/home/root# ./program
AdajfsaSJ_
The characters get echoed on the console. How can I stop this? I know it's theoretically possible, but I can't find out how to implement it.
If you need a better example for what I want to achieve, use the screen command on an empty serial port. screen /dev/tty30 for example. This empties the console and runs the program, HOWEVER, the user is not able to enter any characters (there's a blinking white cursor block and no keyboard characters are being echoed to the console). That's what I need.
Any insight would help, thanks!
Use termios() to turn off the ECHO flag of the terminal.
To turn off the text cursor, use the termcap library to control the cursor visibility.
I'm trying to make a (somewhat) stylish DOS menu as a present for my father.
I was able to get the whole menu system to work, but I wanted to gussy it up with some box drawing characters and, possibly, colored text.
In this YouTube video, the user shows an example of what I'm trying to do (example at the 5:00 mark), but doesn't explain how those characters are being rendered. In the Notepad document, it is displayed as goofy characters.
Do I need to save the file with a special type of encoding? Can it only be done in Notepad (I'm using TextEdit on Mac)? Can someone provide an example menu that can be added to DOSBox's [autoexec] config?
Also, I'm not sure if it is possible, but how can the text color/background color be changed? When running DOSBox initially, it shows their welcome screen with a blue background and box drawing characters, so I would think all of that is possible.
I tried using escaped unicode characters and I tried using a capital-E acute (as shown in the linked video), but they just render funky stuff when run in DOSBox.
The discrepancy in characters is a result of different code pages being used in character rendering. English-speaking Windows uses ANSI code page 1252 (otherwise known as Latin-1), while DOS uses OEM code page 437, or IBM-PC.
The codepage that Windows uses will vary based on your system language, so you many need to experiment to find the correct characters, but basically, find the character you want to print in 437 (say ╔, which is 200) and then in your code use the 1252 version (where 200 is È). Then save the file in ANSI encoding.
I've written a tiny program in Ansi C on Windows first, and I compiled it on Ubuntu with the built-in GCC now.
The program is simple:
read the line from console with scanf().
Analyze the string and calculate.
But something weird happens. When I try to move the cursor, it prints four characters:
pressing Up prints "^[[A"
pressing Dn prints "^[[B"
pressing Rt prints "^[[C"
pressing Lt prints "^[[D"
How can this be avoided?
Why does it print these 4 characters instead of moving the cursor?
Because that's what the keyboard actually sends to the PC (more precisely, what the terminal prints for what it actually receives from the keyboard). bash for example gets those values, deciphers them and understands that you want to move around, so it will either move the cursor (in case of left/right) or use its history to fetch previous commands (up/down). So you can't expect your program to magically support arrow keys.
However, reading from standard input from the terminal already supports left/right arrow keys (I believe, but I'm not in Linux right now to test and make sure). So my guess is that there is another issue interfering. One possible cause could be that one of your modifier keys is stuck? Perhaps ALT, CTRL or SUPER?
For those who are coming from the osx (mac) try changing the shells to bash
Terminal -> Preferences -> Shells open with -> [select] Command (complete path)
then paste
/bin/bash
This might be because the user account is created in shell. You can change it to bash by two ways.
Permament solution is -
sudo chsh -s /bin/bash ${username}
To get this solution working you will have to logout and login
Temporary solution is everytime when you login into the ubuntu server type bash and hit return.
If it's under a docker container, run /bin/bash . This helped me solve the problem.
Additionally to what Shahbaz mentioned, I realized that pressing enter (thus sending an empty command) can fix the problem. This is usually necessary after using CTRLC to cancel a command.
On MacOS Terminal for me was enough to uncheck "Scroll alternate screen" for the issue to disappear. See screenshot of the preferences below.
You can (re)bind keys. Add this at the bottom of your .profile, .zshrc or whatever shell config you have.
bindkey -e
bindkey '\e\e[C' forward-word
bindkey '\e\e[D' backward-word
i think simple way is we can just do
kill %%
because this sometimes happen because of background processes.
I've wrote a simple console program in C which uses ANSI escape codes to color its text.
Is there a way to temporarily set the background of the whole terminal to black and the default font color to light gray? Can this be reverted after the program ends?
I'd prefer to avoid using ncurses.
Probably the simplest way to go is to set the background colour of your text with ANSI:
For instance using:
echo -e "\e[37m\e[41m"
will give you blue text on a red background (you can use this to test the effect in dramatic, easy to see colours).
Whereas
echo -e "\e[97m\e[40m"
will set the foreground to white and the background to black for the duration of your program.
If you find that you're getting a kind of ugly transition zone between your background colour and the terminal's just print a sufficient number of newlines to wipe the whole screen.
To use this in C, you'll obviously want printf instead of echo.
The wiki page on ANSI escape codes has additional information.
How to do this depends on the terminal the user is using. It may be ANSI, it may be VT100, it might be a line printer. ncurses abstracts this horror for you. It uses a database of information about how to talk to different kinds of terminal (see the contents of $TERM to see which one you are currently using) normally stored in /lib/terminfo or /usr/share/terminfo.
Once you look in those files, you'll probably want to reconsider not using ncurses, unless you have specific requirements to avoid it (embedded system with not enough storage, etc.)