[SOLVED] Bash script fails to read the "xclip -o" output's lenght

windowsuser · 04-13-2022, 11:16 PM

I am trying to write the following script to automatically generate and open a QR code whenever a Monero adress (i.e. a string 95 characters long) is in the clipboard.

Code:

xclip -o

correctly provides the clipboard's content. However, the following script, for which ShellCheck did not detect any issues, fails to do it's job and instead keeps the value of the variable which was supposed to store the clipboard's length set to 8, no matter what it contains:

Code:

#!/bin/bash

clipboard="xclip -o"
length=${#clipboard}
echo "$length" #this one is just for testing
if [ "$length" -eq 95 ]; then
	qrencode -o "$clipboard.png"
	xdg-open "$clipboard.png"
fi

ondoho · 04-14-2022, 12:10 AM

Quote:

Originally Posted by windowsuser

I am trying to write the following script to automatically generate and open a QR code whenever a Monero adress (i.e. a string 95 characters long) is in the clipboard.

Code:

xclip -o

correctly provides the clipboard's content. However, the following script, for which ShellCheck did not detect any issues, fails to do it's job and instead keeps the value of the variable which was supposed to store the clipboard's length set to 8, no matter what it contains:

Code:

#!/bin/bash

clipboard="xclip -o"
length=${#clipboard}
echo "$length" #this one is just for testing
if [ "$length" -eq 95 ]; then
	qrencode -o "$clipboard.png"
	xdg-open "$clipboard.png"
fi

"xclip -o" is upposed to be a command, and you want to read the command into a variable, yes?
In that case you have to use

Code:

clipboard="$(xclip -o)"

which I believe is called command substitution.

Other than that your script looks fine (I know nothing about QR codes though), except that bash can do arithmetics more elegantly:

Code:

if [ "$length" -eq 95 ]; then

can become

Code:

if (( length == 95 )); then

michaelk · 04-14-2022, 07:33 AM

Code:

	qrencode -o "$clipboard.png"
	xdg-open "$clipboard.png"

I'm not sure if you want to name your file with your address.

Code:

	qrencode -o "my-address.png "$clipboard"
	xdg-open "$my-address.png"

teckk · 04-14-2022, 10:21 AM

Code:

sudo pacman -S xclip
...
(1/1) installing xclip                              [##########################] 100%
:: Running post-transaction hooks...

https://monerodocs.org/public-address/standard-address/

Code:

xclip -o
4AdUndXHHZ6cfufTMvppY6JwXNouMBzSkbLYfpAV5Usx3skxNgYeYTRj5UzqtReoS44qo9mtmXCqY45DJ852K5Jv2684Rge

clipboard="xclip -o"

length=${#clipboard}

echo "$length"
8

Then this is never going to happen

Code:

if [ "$length" -eq 95 ]; then

Code:

if [ "$length" -eq 95 ]; then
    echo "Yes"
else
    echo "no"
fi

no

windowsuser · 04-14-2022, 05:41 PM

OK it reads the clipboard's length correctly now, though no QR code seems to be generated.

michaelk · 04-14-2022, 05:44 PM

Look at post #3 again

windowsuser · 04-16-2022, 02:23 AM

Apparently the problem was the incorrect placement of the quotation marks in your snippet, but thanks nevertheless. For the past couple of hours I have been tweaking my script and the single-run version of it used to look like this whereas everything seemed to run fine:

Code:

#!/bin/bash
clipboard="$(xclip -o)"
length=${#clipboard}
dircheck() {
	if [[ ! -d "$HOME/XMR Adress book" ]]; then
	mkdir -p "$HOME/XMR Address book" && cd "$HOME/XMR Address book"
	return
	else
	cd "$HOME/XMR Address book"
	fi
}

if [ "$length" -eq 95 ]; then
	dircheck
	echo 'Press n for a temporary QR code (deleted after 10 minutes). To not generate a QR code, press q. Otherwise, type the filename:'
	read -r filename
	        if [ "$filename" = n ]; then
			qrencode -o tmp.png "$clipboard"
			xdg-open "tmp.png"
			xclip /dev/null
			sleep 600
			rm tmp.png
		elif [ "$filename" = q ]; then
			echo "$clipboard " > tmpclip 
			xclip tmpclip
			rm tmpclip
			exit
		else
			qrencode -o "$filename" "$clipboard"
			xdg-open "$filename"
			xclip /dev/null
		fi
	else 
	sleep 60
	exit
	fi

However I am interested in making this script usable by making it run in background. For the past few hours I have been trying to achieve this with a few loops, the hitherto result here. Unfortunately it doesn't seem to work. The bash debugger for vscode is apparently broken and shellcheck doesn't report any relevant problems. So I would highly appreciate any suggestions on how to make it usable and running in background again (I know that I can make a systemd service of it, but it still would require running

Code:

systemctl restart

after it does it's job without proper loops, wouldn't it?

ondoho · 04-16-2022, 03:06 AM

^ I'd recommend to gather a little more knowledge before tackling systemd.

Let's concentrate on a looped script first.
If the script works as such, wrapping it into one(!) endless loop with one(!) sleep should suffice.
Instead you have several sleeps and waiting loops in there. Esp. idle(), which endlessly (?) checks a value that is not read in again.

michaelk · 04-16-2022, 07:54 AM

I assume you are manually copying the address to the clipboard so why not create a keyboard shortcut to create the QR code? Use zenity or something similar to create a popup window if desired for your filename function etc.

Using crontab or systemd timer you could run your script every minute for example but if you copied something to the clipboard and then have to wait 60 seconds for something to happen that would get tedious quickly.

You might be able to use a clipboard manager to run your script once you copy the address but no idea how or what that would take.

pan64 · 04-16-2022, 11:36 AM

Probably I misunderstood, but how do you want to run an interactive script as a service (or background process)?

ondoho · 04-18-2022, 12:36 AM

^ & ^^ both good points that I hadn't noticed/adressed before.
I was thinking a hotkey-based solution: highlight some text (?some 95 char QR code thingy?) and press a hotkey that reads the primary selection right there, asks questions, performs operations.