Is sleep in a while true loop acceptable ?

Hello I have a system that has some commands that need to be manually issued when certain conditions are met.

I monitor journal logs to determine when these conditions are met. My current code is just a few lines. It’s just a while true loop which checks the logs from the last 5 minutes and if it finds the condition it issues the command. After that sequence it just sleeps for 5m

Everything works fine but I’m just wondering if sleep is considered amateur or “bad code” if it is should is there a better way I should do it?

I searched around and it seems like it’s ok since people say it doesn’t really consume cpu cycles. Is that correct?

https://redd.it/109u9mx
@r_bash

scp'ing a file name with spaces in it is driving me crazy

I'm trying to make a tool to scp a file to a remote directory and rename it, but it's not working. The scp works when I do it manually e.g.

scp file.mp4 user@host:/path/to/directory/"new name.mp4"

but with the noscript it always fails with

No such file or directory

or

ambiguous target

When there are no spaces in the file name it works fine, and when I do it manually it works fine using 1x quotes for the file name on the local machine and 2x quotes for the file name on the remote machine. The noscript is like this:

echo "Which file to transfer?"
read noscript
echo "What to save it as?"
read name
scp $noscript user@host:/path/to/folder/'"$name"'

There are 2x quotation marks in the location on the remote machine (I even tried 3x quotation marks). This got the error

<last word of the renamed file name>.mp4" No such file or directory

How do I use variable and name with spaces together in a bash noscript??

Thanks

https://redd.it/109tcyn
@r_bash

Alias to locate for greater ease

Hello.

This isn't great code, but it saves you from typing three commands when your locatedb is out of sync with the filesystem, so it was an idea.

I update the locatedb once per day, but that doesn't seem to be enough, I should probably have it run every 2 hours. And still then, it wouldn't be updated enough for me to find that file I want to locate I reckon.

Finding files with locate is so much faster than with find when you know the file name, or large parts thereof, otherwise I tack on a | grep <something> to filter down the output.

If you don't use locate, and you use the apt package manager, then you can install it by:

sudo apt update && sudo apt upgrade -y && sudo apt install mlocate

Anyways, I made an alias, that took care of running sudo updatedb if locate didn't find the file, in the first place, and then ran locate afterwards, so now I know for sure that the file isn't there, or I may re-spell my search. With only one command, instead of three.

alias locate='suomynona() { locate $1 || sudo updatedb && locate $1 ; unset -f suomynona ; } ; suomynona '

And, I reckon this is within the scope of this subreddit, since we are talking about aliases, but by all means, feel free to reimplement it as a function. :)

And the weird function name, is named that way, so I don't undeclare somebody else's function.

Enjoy!

https://redd.it/109ymzz
@r_bash

"While loop" isn't l going through all variables

Starting to get my hands a little more dirty in bash.


I have a input file that contains a list of hosts that I would like to check if "/dump" is mounted.


Currently the list of host has 18 hosts. All are passwordless accessible.


So I pretty much want to ssh into a server and check to see if "/dump" is mounted or not.



#!/bin/bash

while read hostList; do
result=$(ssh "$hostList" 'mount | grep "/dump"')
if -z "$result" ; then
echo "$hostList: /dump is not mounted"
else
echo "$hostList: /mnt is mounted"
fi
done < hostList


I guess the problem is when I run this noscript sometimes it just comes back with 1 result, like it's only hitting the first hostname in the "hostList". Other times it comes back with the first 3 servers in the "hostList".


I can't seem to get it to hit all 18 servers in the "hostList".

https://redd.it/10a2ew9
@r_bash

Arithmetic Expressions

Hello,

I was hoping someone could explain to me what I am doing wrong here. I am a newbie at bash.

In hackerrank (website) there is a task to display a given expression rounded to 3 decimal places.

___________________

|Sample 1 input: |

\---------------------------

5+50*3/20 + (19*2)/7

\-------------------------------------------------------------------------------

\#my_code

\#!/bin/bash

read A

read B

read C

read D

read E

read F

x=$(( $A+$B * $C/$D + ($E**2) / $F ))

echo $x

&#x200B;

\------------------------------------------------------------------------------

The arithmetic works up until I add /F, then the red error marks occur.

If I try to run it I get the following error:

Solution.sh: line 10: A+B*C/D + (E**2) / F : division by 0 (error token is "D + (E**2) / F ")

I've taken the /F out and then the code runs. Is there an operator or syntax format I'm overlooking?

any additional help would be greatly appreciated.

https://redd.it/10agu8e
@r_bash

Why can the terminal not do syntax highlighting for bash the way VSCode can (or even my note taking app Obsidian.md)?



https://redd.it/10an288
@r_bash

Why can't I pipe into the select command

Hello,

I want to make an user interactive selection within a pipe with

any_producing_commands|select menu_item in $(cat); do echo -n "${menu_item}"; break; done|any_consuming_commands

in between other commands.

Example

seq 0 4|select menu_item in $(cat); do echo -n "${menu_item}"; break; done|wc -c

But this breaks the pipe and just prints me the selection menu.

Can somebody tell me why and if possible provide me a solution?

I know this does work, but I want to be able to pipe parameters into the menu:

select menu_item in $(seq 0 4); do echo -n "${menu_item}"; break; done|wc -c

https://redd.it/10aq82w
@r_bash

ramfetch, now with the ascii logo having 2 notches.
https://redd.it/10b2jo2
@r_bash

Search file by name in specific repo to check whether it exists

My task is to check whether some file with a specific name in an arbitrary repo exists and tell user path to it or return null. I am not sure whether I am looking for in the right direction. I don't see REST method that will allow me to do such task directly in this page.

https://redd.it/10b6fxo
@r_bash

Writing a as-portable-as-possible noscript for downloading and compiling an Analog Clock written in my programming language (called AEC).

I've tried to write a as-portable-as-possible noscript for downloading the source code and building the Analog Clock in AEC.

For AEC-to-x86:

mkdir ArithmeticExpressionCompiler
cd ArithmeticExpressionCompiler
if [ $(command -v wget > /dev/null 2>&1 ; echo $?) -eq 0 ] # Check if "wget" exists, see those StackOverflow answers for more details:
                                                                                         # https://stackoverflow.com/a/75103891/8902065
                                                                                         # https://stackoverflow.com/a/75103209/8902065
then
  wget https://flatassembler.github.io/Duktape.zip
else
  curl -o Duktape.zip https://flatassembler.github.io/Duktape.zip
fi
unzip Duktape.zip
if [ $(command -v gcc > /dev/null 2>&1 ; echo $?) -eq 0 ]
then
  gcc -o aec aec.c duktape.c -lm # The linker that comes with recent versions of Debian Linux insists that "-lm" is put AFTER the source files, or else it outputs some confusing error message.
else
  clang -o aec aec.c duktape.c -lm
fi
./aec analogClock.aec
if [ $(command -v gcc > /dev/null 2>&1 ; echo $?) -eq 0 ]
then
  gcc -o analogClock analogClock.s -m32
else
  clang -o analogClock analogClock.s -m32
fi
./analogClock
        

For AEC-to-WebAssembly:

if [ $(command -v git > /dev/null 2>&1 ; echo $?) -eq 0 ]
then
  git clone https://github.com/FlatAssembler/AECforWebAssembly.git
  cd AECforWebAssembly
elif [ $(command -v wget > /dev/null 2>&1 ; echo $?) -eq 0 ]
then
  mkdir AECforWebAssembly
  cd AECforWebAssembly
  wget https://github.com/FlatAssembler/AECforWebAssembly/archive/refs/heads/master.zip
  unzip master.zip
  cd AECforWebAssembly-master
else
  mkdir AECforWebAssembly
  cd AECforWebAssembly
  curl -o AECforWebAssembly.zip -L https://github.com/FlatAssembler/AECforWebAssembly/archive/refs/heads/master.zip # Without the "-L", "curl" will store HTTP Response headers of redirects to the ZIP file instead of the actual ZIP file.
  unzip AECforWebAssembly.zip
  cd AECforWebAssembly-master
fi
if [ $(command -v g++ > /dev/null 2>&1 ; echo $?) -eq 0 ]
then
  g++ -std=c++11 -o aec AECforWebAssembly.cpp # "-std=c++11" should not be necessary for newer versions of "g++". Let me know if it is, as that probably means I disobeyed some new C++ standard (say, C++23).
else
  clang++ -o aec AECforWebAssembly.cpp
fi
cd analogClock
../aec analogClock.aec
npx -p wabt wat2wasm analogClock.wat
node analogClock

Is there anybody knowledgeable about various operating systems here to know how to make the noscripts better?

https://redd.it/10b64u7
@r_bash

Learning bash. Why isn't this command outputting when the file changes?

I need a noscript that will continuously output the current battery percentage whenever it changes. I looked online and found that I could use the "entr" program to accomplish this. Here's the noscript I wrote.

\#!/bin/bash

capacity_file="/sys/class/power_supply/BAT1/capacity"

echo $capacity_file | entr sh -c "cat $capacity_file"

&#x200B;

I'd expect this noscript to output the current battery percentage when it's ran, and output the updated percentage every time that it changes. When I run the noscript, I'll get the current percentage of the battery outputted, but when the battery discharges some more, the updated value is never printed to stdout. I can tell that the percentage has updated by manually reading the contents of the capacity file.

&#x200B;

As a proof of concept for the noscript, I updated the capacity_file variable to be "./temp". After running the noscript, I can change value of the temp file by running commands like "echo hello > ./temp". When I run these commands, the noscripts shows the updated value every time.

So why is it that this noscript is working in the temp file example, but not with the battery capacity file?

https://redd.it/10btynr
@r_bash

Group files with same name…

I’m scratching my head thinking on how to achieve this and today group files came to my mind, well, if possible.
I have a directory with more than one video file. I need to convert it through ffmpeg and burn in the source timecode in the converted video. For one file I can to this, not for more than one. The thing is that in order to get the timecode I need to run mediainfo that will generate a txt file with the TC for each video file, getting its name, so I will have file01.mov and file01.txt, file02.mov and file02.txt, and so on. The problem is that ffmpeg will only grab one txt file and all the converted videos will end up with the same burnt TC.
Thanks in advance!

https://redd.it/10cdd63
@r_bash

A shell noscript to check the version of NodeJS doesn't work in Git Bash on Windows.

I am trying to make a shell noscript to automatically download, compile and build some program I've made. You can see the full noscript on my blog. My program requires NodeJS 11 or newer, so I am trying to make my noscript output an appropriate error message in case it's not installed. Here is what I've tried:

node_version=$(node -v) # This does not seem to work in Git Bash on Windows.
# "node -v" outputs version in the format "v18.12.1"
node_version=${node_version:1} # Remove 'v' at the beginning
node_version=${node_version%\.*} # Remove trailing ".*".
node_version=${node_version%\.*} # Remove trailing ".*".
node_version=$(($node_version)) # Convert the NodeJS version number from a string to an integer.
if [ $node_version -lt 11 ]
then
  echo "NodeJS version is lower than 11 (it is $node_version), you will probably run into trouble!"
fi

However, when I try to run it in Git Bash on Windows 10, with NodeJS 18 installed and in PATH, here is what I get:

stdout is not a tty
NodeJS version is lower than 11 (it is 0), you will probably run into trouble!

What is going on here?

https://redd.it/10cip05
@r_bash

A more function that uses batcat with a search word, lets you: "man bash | more Readline"

Hello.
It's a simple function, I use batcat I think bat will do just fine.

You get the different color themes by batcat --list-themes and you might get batcat or bat via your packet manager.

It's a rewrap of more into a function, to get color syntax.

No parameters means we are getting stdin.
1 parameter that is a filename; we open file.
1 parameter that isn't: we try searching stdin.
2 parameters where the second isn't a file-name; we search with $1
All other cases, we treat it like filenames.

That's what suits my needs for the moment anyway, if you want to be able to specify many files, with one of the arguments beeing a search parameter, then that should be relatively easy to implement.

# 2023 (c) McUsr -- Vim License
export BATCATTHEME="Monokai Extended Light"
more() {
if [ $# -eq 0 ] ; then
batcat --style header --theme "$BATCATTHEME" --pager less
elif [ $# -eq 1 ] ; then
if [ ! -r $1 ] ; then
# we are going to search what get piped from stdin.
# ex: man bash | more Readline
batcat --style header --theme "$BATCATTHEME" --pager "less -p $1"
else
batcat --style header --theme "$BATCATTHEME" --pager less $1
fi
elif [ $# -eq 2 ] ; then
if [ ! -r $2 ] ; then
if grep $2 $1 &> /dev/null ; then
batcat --style header --theme "$BATCATTHEME" --pager "less -p $2" $1
else
batcat --style header --theme "$BATCATTHEME" --pager less $1
fi
else
batcat --style header --theme "$BATCATTHEME" --pager less $1 $2
fi
else
batcat --style header --theme "$BATCATTHEME" --pager less $
fi
}

Enjoy.

https://redd.it/10cj5xq
@r_bash

Noob While Loop Only Reads Last Line Correctly

I'm trying to loop through newlines in a file and print both its text and row count.

However, it only shows correctly on the last line, probably because of [ -n "$line" ]. I noticed that switching around "$line" "$i" would fix this error, but I need it to be formatted like the code since I'm passing the result into another command.

Code:

i=0
while IFS= read -r line; -n "$line" ; do
echo "$line" "$i"
i=$((i + 1))
done < "$1"

Text:

Apple
Banana
Coconut
Durian

Need:

Apple 0
Banana 1
Coconut 2
Durian 3

Error:

0ple
1nana
2conut
Durian 3

https://redd.it/10cw5ap
@r_bash

Make Neofetch update hard-linked image

TL;DR How can I make Neofetch update a hard-linked image without reboot?

So I have Neofetch configured to display an image which it does perfectly. The image is a graph, which is created / overwritten by a python noscript which I update daily. The image in the directory displays perfectly up-to-date, while Neofetch is still using an out-of-date version of the graph / image.
Any tipps how I could make Neofetch update the image? Is it stored somewhere for Neofetch to use, cause if so I could probably integrate deleting such backup in my noscript.

SOLVED:
Typical case of feeling stupid, just minutes after posting, where the question already contains the path to the answer:
in the neofetch config we find the path to the thumbnails folder home/user/.cache/thumbnails/neofetch
Of course after wiping the contents of the folder, a new instance of neofetch will get a fresh version of the image and everything works smoothly. I will integrate deleting the content of the thumbnails folder into my noscript and everything will be fine.
Hope this helps anybody though

https://redd.it/10da4sh
@r_bash

Bash Scripting - If statement always returns truthy value

Hi all,

I have been facing an issue with my bash noscript where the "if" statement always returns true, even when the condition is not met. Here is the noscript:

#!/bin/bash

#Required to be able to use "nvm" in a shell noscript
export NVM_DIR=$HOME/.nvm;
source $NVM_DIR/nvm.sh;

# Check if Node is already at the latest version
CURRENT_NODE_VERSION=$(nvm current)
LATEST_NODE_VERSION=$(nvm ls-remote --lts | grep 'Latest LTS: Hydrogen' | awk '{print $2}')

if [ "$CURRENT_NODE_VERSION" != "$LATEST_NODE_VERSION" ]; then

  echo "Updating Node"
  nvm install --lts=Hydrogen --reinstall-packages-from="$CURRENT_NODE_VERSION"
  nvm use --lts
else
  echo "Node is already up to date"
fi

# Check if npm is already at the latest version
echo "Updating npm global packages"
npm update -g --depth 0

Could anyone please help me understand why this is happening and how to fix it?

Thank you

https://redd.it/10d9712
@r_bash

question, how to make sure that line of command will not stop the rest of noscript .

there && that make sure the next command will run either the earlier one is executed or not.

i need to put like of two command , how to make sure then those two command 'all in 1 line' if they not executed , the rest of the noscript will keep continue and not affected by this line ?

for instance a line with 'date && cal' .

if those by any chance not executed how to make sure the rest of the noscript will continue ?

should i add what at the end of the line or just as it is will not halt the rest of noscript weather such a line like this 'COMMAND && COMMAND' executed or not ?

https://redd.it/10dhdcg
@r_bash

Why can't I operate on the return of my ssh call using the eq comparison operator?

Hello, I've got a problem with using the return of an ssh call and comparing it with numbers and thought maybe someone can help me.
I have two different calls that I make in a noscript, one of them is a mkdir call like this:
RET=ssh user@system -t "mkdir -p <path>"
And the other one does the following
RET=ssh user@system -t "ls -l <path>"

When I now call $?, I will get a 0 in both cases if the command has been executed successfully, but if I want to compare that 0 with the eq (or -eq) operator, I get an error in the first command, but not in the second.
I get that -eq is used to compare numbers, which I assumed is what is getting returned.
Is there any explanation that I'm not seeing why the first command isn't return such a number but rather a string?

If I use the != operator, I can do the comparison no problem, but not with eq.

Any ideas?

https://redd.it/10dg0s2
@r_bash

Is there a good way to programmatically determine how many inputs some function can support?

WHAT I WANT TO DO

Programs like sha256sum accept a list of inputs and will apply whatever the function does (e.g., compute the sha256sum) to each (non-option) input independently. You can do, for example:

sha256sum file1 file2 file3 ...

or

find ./ -type f | xargs -P<N> sha256sum

Other programs, for example, basename, only support 1 non-option input. you cant use

basename file1 file2 file3 ...

nor

find ./ -type f | xargs -P<N> basename

instead, you have to use

for file in file1 file2 file3 ...; do
basename "$file
done

or

find ./ -type f | xargs -l1 -P<N> basename

Im trying to figure out a good way to determine, for some generic function, which of the above is the case (and in the "multiple inputs" case what the maximum number of inputs is) without requiring any user interaction.

Any good way to do this?

WHY

I put together a shell function for parallelizing loops called forkrun. Instead of forking off individual processes it initially forks off N coprocs (for N worker threads) and then pipes data to them. Its usage is much the same as using parallel or xargs -P, though with fewer bells and whistles (it has flags that support changing the number of parallel worker threads and producing output that is ordered the same as the inputs).

Right now it sends 1 input at a time to the worker coprocs, making it equivalent to xargs -l1 -P<N>, an d comared to xargs -l1 -P<N> it is considerably faster (4-5x on my hardware). BUT, xargs -P<N> is still ~2x as fast (but only works on functions like sha256sum that accept many inputs). I could add a user parameter to set how many lines to group together and send to the worker coprocs (much like xargs -L parameter), but would like to, if possible, be able to dynamically choose an optimal value for this on a function-by-function basis.

https://redd.it/10dtkao
@r_bash

Is there a good way to programmatically determine how many inputs some function can support?

WHAT I WANT TO DO

Programs like sha256sum accept a list of inputs and will apply whatever the function does (e.g., compute the sha256sum) to each (non-option) input independently. You can do, for example:

sha256sum file1 file2 file3 ...

or

find ./ -type f | xargs -P<N> sha256sum

Other programs, for example, basename, only support 1 non-option input. you cant use

basename file1 file2 file3 ...

nor

find ./ -type f | xargs -P<N> basename

instead, you have to use

for file in file1 file2 file3 ...; do
basename "$file
done

or

find ./ -type f | xargs -l1 -P<N> basename

Im trying to figure out a good way to determine, for some generic function, which of the above is the case (and in the "multiple inputs" case what the maximum number of inputs is) without requiring any user interaction.

Any good way to do this?

WHY

I put together a shell function for parallelizing loops called forkrun. Instead of forking off individual processes it initially forks off N coprocs (for N worker threads) and then pipes data to them. Its usage is much the same as using parallel or xargs -P, though with fewer bells and whistles (it has flags that support changing the number of parallel worker threads and producing output that is ordered the same as the inputs).

Right now it sends 1 input at a time to the worker coprocs, making it equivalent to xargs -l1 -P<N>, an d comared to xargs -l1 -P<N> it is considerably faster (4-5x on my hardware). BUT, xargs -P<N> is still ~2x as fast (but only works on functions like sha256sum that accept many inputs). I could add a user parameter to set how many lines to group together and send to the worker coprocs (much like xargs -L parameter), but would like to, if possible, be able to dynamically choose an optimal value for this on a function-by-function basis.

https://redd.it/10dtkao
@r_bash