wjandrea's questions

I accidentally ran less with an empty filename, which I expected to fail, but to my surprise, it printed some environment variables:

$ less -XE ""
export LESSOPEN="| /usr/bin/lesspipe %s";
export LESSCLOSE="/usr/bin/lesspipe %s %s";

(-XE basically makes it behave like cat.)

cat, on the other hand, fails:

$ cat ""
cat: '': No such file or directory

And if you leave out the filename entirely, less does error:

$ less -XE
Missing filename ("less --help" for help)

Why does less do this? I can only imagine it being problematic, because if there's some bug in your code that causes an empty filename, you'll get bogus output. (Like, say, less "$(which nonexistent-script)".)

While we're here, why does it print those environment variables? Are they from my environment? They're identical:

$ declare -p LESSOPEN LESSCLOSE 
declare -x LESSOPEN="| /usr/bin/lesspipe %s"
declare -x LESSCLOSE="/usr/bin/lesspipe %s %s"

I checked man less but the filename parameter doesn't seem to be documented explicitly. Other mentions of it didn't seem to be related to this behaviour. I also checked the less FAQ.

I just installed an IDE extension that runs the current program in a terminal, and I have Gnome Terminal set to stay open when the command exits, but when that happens, the first two lines are covered up by the message "The child process exited normally with status 0". How could I move it?

I believe this is possible by editing a Gnome stylesheet, but I'm not sure where to start.

Example

Here's a simple Python script:

#!/usr/bin/env python3

x = input('Enter something: ')
print('You entered:', x)

I run it and type something:

(My system is in French.)

Then as soon as I press Enter, the script exits and the message pops up, blocking the output:

I'd rather have the message somewhere else, like at the bottom for example. Here's a mockup:

You can reproduce the issue by saving the script as tmp.py then running gnome-terminal -- python3 tmp.py. And make sure you have Gnome Terminal set up correctly: go to Edit → Preferences → Command → When the command exits and select Hold the terminal open.

Possible workarounds

• Make the program hold the terminal open, e.g. input('Press Enter to finish...'). -- I'd rather not have to put that on everything I write.
• Use an integrated IDE terminal. -- I haven't found a good one yet, and I prefer using the native terminal for most things.
• Relaunch the program after it exits. -- If it has any side-effects, that might be bad, for example if it reads and writes any files.

Related

• Avoid the yellow message at the top of the gnome-terminal window that states "The child process exited normally with status 0."

Some scripts I wrote show notifications like "Volume up" or "Reset brightness" for example, using notify-send. However, the notifications get saved in the notification menu on Ubuntu 18.04, which I don't want since there are so many repeats. How do I prevent that?

Here's what I tried:

• Checked man notify-send but didn't see any options about not saving the notification.
• notify-send --urgency=low - no difference
• Researched "gnome toast notifications" but apparently they're application-specific, which doesn't work for me
• Considered using Zenity but I couldn't find a way to make a notification that doesn't steal focus.
• In Python, making a Notify.notification object .show() twice - no difference

If you type something in Gedit then erase it and try to close Gedit, it will ask if you want to save the file, even though it's blank. Is there a way to avoid this? Notepad++ and Atom for example do this by default.

I've checked through Gedit's preferences, man gedit, and did a quick Google but couldn't find anything related.

I'm using the default Gedit 3.28.1 on Ubuntu 18.04.

Using xdotool type or xdotool key with certain characters makes Gnome Shell lock up. For example typing a single slash with xdotool type / or xdotool key slash takes a second or two, but for something like 23 slashes (i.e. xdotool type ///////////////////////) it's more than 25 seconds.

Of all the printable ASCII characters, only these cause the problem:

• slash /
• backslash \
• bar |
• bracketleft [
• bracketright ]
• braceleft {
• braceright }

Outside ASCII, I've only tested çé°†, but they also cause the problem.

Why does this happen and how can I fix it?

More details

I never had this problem in Unity on 14.04.

There is a small delay when typing other characters, but only up to a second, even for long strings.

Any timing I've done in the terminal has come back normal, like time xdotool type ... or t=$SECONDS; xdotool ...; echo $((SECONDS-t)), so it seems to be a problem on Gnome Shell's side.

I've confirmed $XDG_SESSION_TYPE is x11.

If I run apt-cache show nonexistent, I get this error:

N: Unable to locate package nonexistent
E: No packages found

I know the E stands for "Error", and a W would stand for "Warning", but what does the N stand for? "Information"?

Are there other letters that may show up?

I couldn't find anything in man apt-cache, man apt, or man apt-get.

P.s. This came up because of this question: Bash file redirection bug?

I'm editing my PS1 prompt and I don't want to keep sourcing my bashrc to update it (since my bashrc resets other things too). I also don't want to copy and paste it over and over. Is there a way to edit the variable interactively, like using nano (my default editor)?

The PS1 is mostly an example, because I want to do the same thing with other vars. The reason I want to do it interactively is that the variable is already quite long, and I just need to edit a few characters in it. And I only need to change it in the current shell.

When I run less on some file, the prompt goes away, and I get the contents of the file on screen. Then when I press q, it goes back to the prompt. I think less does this by saving the current terminal buffer, opening a new buffer, outputting the file into the new one, then when closed, discarding the new buffer, and restoring the old, but I don't know what this process is called or how it does this.

I looked in man less but didn't find anything. I tried googling it, but couldn't find anything useful, except that the screen command can do the same thing with shell sessions.

Ultimately, I'm asking because I want git diff to use a new buffer instead of printing inline. I've already set GIT_PAGER=less and git --paginate diff, but they didn't change anything. And I have a workaround, but it's a bit long: git diff --color=always | less -R

Update: After some research, it looks like tput smcup and tput rmcup are high-level commands to do the same thing, probably using the termcap package.

As the title says, how can I create a new Gnome Terminal profile?

I want to learn an Irish Gaelic song, but the phonology is making my brain hurt. Here's a line:

’Sé mo Shaesar, ghille mear

Pronounced like:

/ʃe mo hezər ɣɪlə mar/

Is there a program that can convert the lyrics to the International Phonetic Alphabet?

My Logitech H800 normally works fine with Ubuntu, but sometimes, I think when I unplug and replug the USB adapter, it stops working. It is listed in sound settings under outputs, and clicking it highlights it, but sound is still played through the builtin sound hardware. Running pactl list sinks does not show it.

My workaround is running pactl exit, after which all works fine. I just discovered it now but I don't expect it will be a permanent fix.

My internal backup drive is mounted, but when I try to start a backup, or recover missing files, I get the above message. It also says "Waiting for [device] to become available" (translated from French).

This similar question was not useful. I tried creating a folder called "deja-dup" on the backup device, but nothing changed. I have also tried unmounting and remounting the drive.

I have a bunch of functions stored in ~/.bash_functions, which is sourced by ~/.bashrc on shell startup. The file exports all the functions like so:

# Find functions in this script based on a grep search, and export them.
grep ^'[[:alnum:]]' ~/.bash_functions |
  grep '()' |
  cut -d'(' -f1 | 
  while read function
do
  export -f "$function"
done
unset function

This works perfectly fine on a local shell, but not via SSH. None of the functions are actually exported (checked using declare -F). However, if I put echo "$function" into the loop, it prints all the function names, so I know the only part of the loop not working is the export line.

The functions get exported properly if I use export -f in the SSH session, or if I add an export -f line for each individual function in the file.

I'm using 14.04 with Bash 4.3.11, and the SSH client is Termux on Android.

Edit: Even if I add declare -F at the bottom of ~/.bash_functions, the functions show as not exported.

Edit: I just realized that in a local session, some of my functions aren't exported, seemingly at random, but I can't find any evidence of an error. I am doing more research...

My sound card doesn't support midi, but I want to write music in TuxGuitar and listen to the midi output on the fly. Is there some program I can install to do this?

Right now my workaround is to export the files to .MID, then convert them to .MP3 using this command:

timidity "$file" -Ow -o - | ffmpeg -hide_banner -loglevel panic -i - -acodec libmp3lame -ab 128k "${file[@]/%.mid/.mp3}"

I want to make a keyboard shortcut that changes the volume with exactly the same behaviour as pressing one of the default volume keys (up, down, mute), including the OSD notification and the "pop" sound. Right now, my bodged method is to have xdotool press the volume key, but it would be simpler to find the command the default volume keys send when pressed.

I don't want to use unity-control-center to reassign the volume keys, because I want to leave the default volume keys in place.

I have two audio outputs: one is a wireless headset, the other is my laptop's built-in 3.5mm jack. How do I switch between them via the terminal? Ultimately, I want to assign a keyboard shortcut to do the switch.

I'm trying to make a shortcut to send, for example, the universal quantifier symbol, ∀ (U+2200). Xdotool's own documentation doesn't really explain this.

I have my Ubuntu installed on an SSD, and a secondary HDD called Earth that I've set to automatically mount at startup. The thing is, when it mounts, the folder is labelled "Earth1" instead of "Earth". There is still a folder in /media/username called "Earth" but when I attempt to open it, it gives the error:

This location could not be displayed. You do not have the permissions necessary to view the contents of 'Earth'.

So right now a whole bunch of programs are trying to access files in /media/username/Earth but returning errors.

This has been happening since I had a problem with Unity and had to reset some of my user settings. I'm currently logged in as admin, and I've checked the startup command and everything's fine there.

Update 2017-10-31 (for future reference)

I was using Startup Applications to mount Earth (BTW, Startup Applications runs at login, not at boot). Based on subin's answer, I switched to using the Disks utility, which saves its config to the /etc/fstab file (which tells the system to mount partitions at boot), and that worked fine. The fstab entry specified the mount point.

I'm trying to set my numpad to be a media control centre. I want to have the 0 key pull up Clementine and bring it to the foreground. Right now I have it set to launch Clementine, but it just dances in the launcher and doesn't come to the foreground. So, I have Clementine pinned to the second slot on the launcher, and I want to set up a custom key shortcut via the Keyboard Settings. The question is, how do I send Super+2 as a command?

Second, I want the plus and minus keys to send Alt+Left and Alt+Right (for browser navigation).

Third, and less important, I want the period key to open Clementine's EQ, and 7 and 9 to send Fast Forward and Rewind.