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AbstProcDo's questions

Martin Hope
AbstProcDo
Asked: 2019-10-30 00:25:33 +0800 CST
  • 4

The Quick Tile Window keyboard shortcut Super+Arrow left makes the window in focus occupy the left half of the screen. Super+Arrow right makes the focused window occupy the right half.

By using these two shortcuts, two windows occupy space in a 1:1 ratio.

How can I modify these shortcuts to have the left window occupy 45% and the right window 55%?

kde plasma-5 tiling
Martin Hope
AbstProcDo
Asked: 2019-10-18 17:52:18 +0800 CST
  • 31

According to this question, How can I convert a series of images to a PDF from the command line on linux?, ImageMagick can convert multiple images to a single PDF.

How could I reverse the operation and convert a PDF of several pages to multiple images?

I have tried the following command, but I got the errors shown:

$ convert test.pdf test-%02.png
convert-im6.q16: attempt to perform an operation not allowed by the security policy `PDF' @ error/constitute.c/IsCoderAuthorized/408.
convert-im6.q16: no images defined `test-%02.png' @ error/convert.c/ConvertImageCommand/3258.

gs was installed:

$ gs --version
9.26

Ubuntu version:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 19.04
Release:    19.04
Codename:   disco
imagemagick convert-command 19.04
Martin Hope
AbstProcDo
Asked: 2019-10-18 16:27:51 +0800 CST
  • 2

I try to set Bing's Picture of the Day as default Wallpaper.

enter image description here

It did not work as expected.

The other provides

enter image description here enter image description here

My machine info:

$ neofetch --stdout
------------
OS: Ubuntu 19.04 x86_64
Host: MacBookPro11,1 1.0
Kernel: 5.0.0-31-generic
Uptime: 1 hour, 53 mins
Packages: 2374 (dpkg), 4 (snap)
Shell: bash 5.0.3
Resolution: 2560x1600
DE: KDE
WM: KWin
Theme: Breeze [KDE], Breeze [GTK3]
Icons: breeze [KDE], breeze [GTK3]
CPU: Intel i5-4258U (4) @ 2.900GHz
GPU: Intel Haswell-ULT
Memory: 2703MiB / 3850MiB
kde wallpaper kubuntu
Martin Hope
AbstProcDo
Asked: 2019-06-21 16:39:54 +0800 CST
  • 4

Upon trying to start dropbox, it prompts 

$ dropbox start
Starting Dropbox...
The Dropbox daemon is not installed!
Run "dropbox start -i" to install the daemon

Following the instructions, 

$ dropbox start -i
Starting Dropbox...Traceback (most recent call last):
  File "/usr/bin/dropbox", line 1443, in start
    download()
  File "/usr/bin/dropbox", line 294, in download
    import gi
ModuleNotFoundError: No module named 'gi'

Then tried to install gi 

$ pip install gi
Collecting gi
  Could not find a version that satisfies the requirement gi (from versions: )
No matching distribution found for gi

The version:

$ lsb_release  -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 19.04
Release:        19.04
Codename:       disco
dropbox
Martin Hope
AbstProcDo
Asked: 2019-05-29 02:17:02 +0800 CST
  • 4

I tested the single quote and double quotes in sed

me@host:~:
$ echo "front" | sed "s/front/back/"
back
me@host:~:
$ echo "front" | sed 's/front/back/'
back

They performed identically, but I remembered to read there exist differences between them months ago.

Google search not helpful with keywords "single quotes and double quotes in sed".

They are not identically, right?

bash sed
Martin Hope
AbstProcDo
Asked: 2019-05-22 03:49:13 +0800 CST
  • 15

Every time starting the machine, I run the following program:

$ cat start.sh
#! /bin/bash
google-chrome &> /dev/null &
lantern &> /dev/null &
xdg-open . &> /dev/null &
emacs &> /dev/null  &
code ~/Programs/ &> /dev/null &
xdg-open ~/Reference/topic_regex.md &> /dev/null &

Cumbersome &> /dev/null &... How could I shorten the logic?

command-line bash redirect background-process
Martin Hope
AbstProcDo
Asked: 2018-04-14 20:58:15 +0800 CST
  • 3

The the simpler form of a function is:

name () { commands return }

I find no difference in a function with and without return.
Suppose the minimal code:

step_forward (){
    echo "step one;"
    return
}
turn_around() {
    echo "turn around."
    return
}

step_forward
turn_around

Run and check the exit status:

$ bash testing.sh
step one;
turn around.
$ echo $?
0

Run it again after commenting out return

$ bash testing.sh
step one;
turn around.
$ echo $?
0

In what circumstances should a function end with a return?

bash
Martin Hope
AbstProcDo
Asked: 2018-04-12 00:23:34 +0800 CST
  • 27

A function is defined as:

do_something () {
    do it
}

I could understand its name 'do_something' and the curly bracket to encapsulate the actions code, but am unable to get the idea what's the purpose of () here, since there are no named parameters in Bash scripts. It might be better and straightforward to define it as 

do_something {
  do it
}

Which does not conflict with its current syntax, and even more declares that there are no named parameters. What's the usage of () here?

bash
Martin Hope
AbstProcDo
Asked: 2018-03-27 08:25:40 +0800 CST
  • 4

Command grep will print a line when the line contains a string that matches an expression, which is not handy to search for specifed content.

For instance, I have vocabulary files with formatting

**word**
1. Definition:
2. Usage
3. Others

I'd like to retrieve all the words to make a wordlist within files

grep '\*\*[^*]*\*\*'

Returns the bulk of the content.

How to use grep to catch only the word?

command-line grep text-processing
Martin Hope
AbstProcDo
Asked: 2018-03-27 02:57:04 +0800 CST
  • 13

Run Command ls on Current Directory and get the output:

$ ls
Applications Documents    Library      Music        Public
Desktop      Downloads    Movies       Pictures

I'd like to enumerate them like:

1. Applications
2. Desktop
3. Documents
4. Downloads
5. Library
6. Movies
7. Music
8. Pictures
9. Public

This could be achieved using less in an intermediate way

ls | less -N

How to enumerate them in a straightforward way?

command-line