Make dirname -z accept nul-delimited input?

I store an array files containing list of file names that will later be used for further processing (files need to be absolute paths since I reference them elsewhere). For example, I want to determine the minimum amount of mkdir -p arguments to re-create the directories where these files belong.

My files don't have newlines in them but they should still be nul-delimited for good practice. I have the following but the last line doesn't work with error warning: command substitution: ignored null byte in input because I think nul characters can't be in a string:

# Store files in 'files' array
while IFS= read -r -d '' f; do
files+=("$f")
done < <(fd --print0 --base-directory "$rootdir" . "$rootdir" )

# TODO determine minimum amount of directories needed as arguments for mkdir -p
dirname -z "$(printf "%s\0" "${files@}" | sort -zu )" | tr '\0' '\n'


Anyway, a solution is dirname -z -- "${files[@]}" | sort -zu | xargs -0 mkdir -p -- but I'm more curious on the general approach to similar problems with handling nul-delimited items since is is prevalent in noscripting in general:

Is the above with `xargs -0` the go-to simplest noscripting solution whenever you want to pass items that should be nul-delimited as arguments? And that all commands involved should use `-print0`, `-z`, etc. and if an application doesn't support that, you would have to convert it by using something similar to the while loop above? In most of my noscripts, I assumed filenames don't contain newline characters so I never needed to use xargs since most applications assume items are space or newline-delimited. Should xargs dependency be avoided or it's prevalent and useful in general noscripting, something that is used liberally?

What would a (reasonably) Bash (or maybe even POSIX) way to accomplish the same thing?

https://redd.it/1cjdgte
@r_bash

Roman Numerals to Hindi-Arabic Numerals Convertor

### Here is my working attempt at making a roman numerals convertor noscript:

#!/bin/bash
# vim: foldmethod=marker

function romanToArabic {
local input=$1
local result=0
local prevChar=""
local currChar=""
local currValue=0
local prevValue=0

for ((i=0; i<${#input}; i++)); do
currChar="${input:i:1}"

case $currChar in
"I") currValue=1 ;;
"V") currValue=5 ;;
"X") currValue=10 ;;
"L") currValue=50 ;;
"C") currValue=100 ;;
"D") currValue=500 ;;
"M") currValue=1000 ;;
) continue ;;
esac
# Comment{{{
# For numbers such as IV
# The loop first executes the else block
# since there is no prevValue yet.
# so 1 is added to the result variable
# but in the case of IV and such the second iteration
# executes the if block, and so we have to substract 2
# from the result variable. 1 for the incorrect addition
# and 1 for the current number.
# }}}
if ((prevValue < currValue)); then
result=$((result + currValue - 2 prevValue))
else
result=$((result + currValue))
fi

prevChar="$currChar"
prevValue="$currValue"
done

echo "$result"
}

if [ -z "$1" ]; then
echo "Usage: $0 <inputFileorromanNumerals>"
exit 1
fi

if [ -f "$1" ]; then
inputFile="$1"

while IFS= read -r line; do
eval "line=$(echo "$line" | sed -E 's/(IVXLCDM+)/$(romanToArabic "\1")/g')"
echo "$line"
done < "$inputFile" > "$inputFile.tmp"

mv "$inputFile.tmp" "$inputFile"

echo "Roman numerals converted in $inputFile"
else
romanNumerals="$1"
arabicNumber=$(romanToArabic "$romanNumerals")
echo "Roman numerals '$romanNumerals' converted to: $arabicNumber"
fi

https://redd.it/1cje7bw
@r_bash

var3 = var1 || var2

How to write that in Bash ?

Thanks

https://redd.it/1cjlj3s
@r_bash

Screwd up my prompt
https://redd.it/1ck0ma3
@r_bash

History for current directory???

I just had an idea of a bash feature that I would like and before I try to figure it out... I was wondering if anyone else has done this.
I want to cd into a dir and be able to hit shift+up arrow to cycle back through the most recent commands that were run in ONLY this dir.
I was thinking about how I would accomplish this by creating a history file in each dir that I run a command in and am about to start working on a function..... BUT I was wondering if someone else has done it or has a better idea.

https://redd.it/1ckm4ud
@r_bash

How to generate a random string using a seed phrase?

I am looking for a way to generate a random string using a seed phrase in the MacOS Terminal.

Ideally, I am looking for a solution that does not require any libraries/packages that need to be installed.

I also want to be able to specify the character set.

Is this possible with Bash?

https://redd.it/1ckx3o2
@r_bash

adding newline to two variables

Hello all,

In the below snippet, I'm trying to combine the output of 2 external output with a new line between the two output.

Desired output:
both:
f1
f2
f3
f4
Current output:
both:
f1
f2f3
f4

#!/bin/bash

mkdir /tmp/dir1 /tmp/dir2
touch /tmp/dir1/f1 /tmp/dir1/f2
touch /tmp/dir2/f3 touch /tmp/dir2/f4

# nl=$(echo "\n")
nl=$(echo)
# nl=$(echo -e "\n")

dir1="$(ls -1 /tmp/dir1)"
dir2="$(ls -1 /tmp/dir2)"
echo dir1:
echo "$dir1"
echo dir2:
echo "$dir2"
#both="$(echo "$dir1$nl$dir2")"
both=$(echo "$dir1$nl$dir2")
#both="${dir1}\n${dir2}"
echo both:
echo "$both"

https://redd.it/1cl0s1h
@r_bash

Wrote my first bash noscript, looking for someone to look it over and make sure I am doing things correctly

I wrote my first bash noscript, a noscript to back up my linux system. I am going to have a systemd timer run the noscript daily and was hoping someone could tell me if I am doing ok.

Thanks
Suzie

#!/usr/bin/bash

######Define noscript variables

backupdest=/mnt/Backups/$(cat /etc/hostname)
filename=$(date +%b-%d-%y)

######Create backup tar archive

if ! -d "$backupdest" ; then
mkdir "$backupdest"
fi

#######Create tar archive

tar -cpzf "$backupdest/$filename" --exclude={\
"/dev/",\
"/proc/",\
"/sys/",\
"/tmp/",\
"/run/",\
"/mnt/",\
"/media/",\
"/lost+found",\
"/usr/lib/",\
"/usr/share/",\
"/usr/lib/",\
"/usr/lib32/",\
"/usr/include/",\
"/home/suzie/.cache/",\
"/home/suzie/.cmake/",\
"/home/suzie/.config/",\
"/home/suzie/.var/",\
} /


######Delete previous weeks daily backup

find "$backupdest" -mtime +7 -delete

########Create Weekly folder

if ! -d "$backupdest/weekly" ; then
mkdir "$backupdest/weekly"
fi

########Copy Sundays daily backup file to weekly folder

if $(date +%a) == Sun ; then
cp "$backupdest/$filename" "$backupdest/weekly"
fi

########Delete previous months weekly backups

find "$backupdest/weekly" +31 -delete

########Create monthly folder

if ! -d "$backupdest/monthly" ; then
mkdir "$backupdest/monthly"
fi

########Copy backup file to monthly folder

if $(date +%d) == 1 ; then
cp "$backupdest/$filename" "$backupdest/monthly"
fi

########Delete previous years monthly backups

find "$backupdest/monthly" +365 -delete

https://redd.it/1clexd4
@r_bash

how to get a unique emails?

so in this noscripts there are emails in all_emails variable and i want to get the unique ones. this noscript does not work. any suggestions?

for email in "$allemails"; do
        if [[ "$email" -eq "$allemails" ]]; then
        echo "$email - not unique"
        else
        echo "$email - unique"
        fi
    done


https://redd.it/1cln8nr
@r_bash

Why my following noscript doesn’t provide any output?


file=()
while read -r -d ''
do
file+=(“$REPLY”)
done < <(find . -print0)

echo “${file[@]}”


https://redd.it/1clrl3g
@r_bash

Bash AWS kungFu migrating AWS Lambda functions from the Go1.x runtime

I have been working on Migrating AWS Lambda functions from the Go1.x runtime to the custom runtime on Amazon Linux 2, Created the sprint noscript to list lambda func in all region

https://github.com/muhammedabdelkader/Micro-Sprint/blob/main/reports/list\_lambda.sh

Don't forgot the filter command

https://redd.it/1cm6g5v
@r_bash

netcat as non root

With the help of this sub, I was able to get my netcat command to run as expected

printf '#011001\015\012' | netcat -N 192.168.x.x 8080

works perfectly....as root

but I need to be able to run it as a non root user. While it will execute, it does not actually do anything. I cannot figure out why

I have even tried via sudo or su and it just will not execute

Any suggestions to get this to work as a regular user?

I see no errors or why it won't send the commands. I am assuming this is for security reasons...

https://redd.it/1cmaqw6
@r_bash

Settings $PS1 Variable (Prompt String)

In Linux, the bash shell allows you to customize the command prompt that appears before each new line in your terminal. This is done using special prompt variables that are expanded by the shell when it displays the prompt. Here are some of the most commonly used prompt variables:

1. \u - The username of the current user.
2. \h - The hostname up to the first dot. For example, if the hostname is "example.com", then "\\h" will expand to just "example".
3. \W - The basename of the current working directory, with $HOME abbreviated with a tilde (\~).
4. \w - The full pathname of the current working directory, with $HOME abbreviated with a tilde (\~).
5. \$ - A dollar sign ($) for regular users or a hash symbol (#) for the root user.
6. \! - The history number of this command.
7. \t - The current time in 24-hour HH:MM:SS format.
8. \T - The current time in 12-hour hh:mm:ss format.
9. \@ - The current time in 12-hour am/pm format.

You can use these variables to create a custom prompt string by enclosing them in curly braces and separating them with escaped spaces (\\ ). For example, the following prompt variable sets the prompt to display the username, hostname, current directory, and a dollar sign:

export PS1="\u@\h \W\$

https://redd.it/1cmbo6o
@r_bash

Add last login time and elapsed time since current login to prompt in Linux

# Customizing Your Bash Prompt

How to calculate the time of the last login and the time elapsed since the active login in Linux? How do we add them to the $PS1 prompt string variable? This video shows how to do these two things by editing the .bashrc file.

Watching video on YT

https://youtu.be/2uG1Pm3i974

https://redd.it/1cmcyk2
@r_bash

when do you use commands with ./ . ?

Hi! sawing videos about grep command I saw a comand ending in .... grep keytofind ./.

I think that ./ isn't used but maybe I am wrong, when do you use that ./

I know the meaning of ./ but I use in command line go there and then put the commands for example ls , so why should I use there ./

star key.star key = all

Thank you and Regards!

edit by wrong interpretation of star key and markdown

https://redd.it/1cmiaac
@r_bash

Sending and executing a command in the bash noscript and calculating the execution time


# What is the $@ variable in bash?

In Bash noscripting, "$@" is a special variable that represents all the command-line arguments passed to the noscript or function. It allows you to access each argument individually.

Here's an example to illustrate its usage:

#!/bin/bash

# Loop through all the command-line arguments
for arg in "$@"; do
echo "Argument: $arg"
done

If you run this noscript with the command ./noscript.sh arg1 arg2 arg3, it will output:

Argument: arg1
Argument: arg2
Argument: arg3

In the noscript, "$@" expands to separate arguments, so the for loop iterates over each argument and prints it.

We can send a command along with its options through the $@ variable as input to the bash noscript to be executed inside it.

./noscript ls -l (arg1=ls, arg2=-l)
./noscript find / -type f (arg1=find, arg2=/ arg3=-type arg4=f)

It's worth noting that "$@" is different from "$*" in Bash. While "$@" treats each argument as a separate entity, "$*" treats all the arguments as a single string separated by the first character of the IFS (Internal Field Separator) variable (usually a space)

# What is the $SECONDS variable in bash?

In Bash noscripting, $SECONDS is a special variable that holds the number of seconds since the noscript started running or since the last reset of the variable.

Here's an example to demonstrate its usage:

#!/bin/bash

echo "Script started."

sleep 5

echo "Elapsed time: $SECONDS seconds."

sleep 3

echo "Elapsed time: $SECONDS seconds."

SECONDS=0

sleep 2

echo "Elapsed time (after reset): $SECONDS seconds."

When you run this noscript, it will output:

Script started.
Elapsed time: 5 seconds.
Elapsed time: 8 seconds.
Elapsed time (after reset): 2 seconds.

In the noscript, $SECONDS is used to track the elapsed time. It starts counting when the noscript begins executing, and you can access its value using $SECONDS at any point in the noscript.\\

By resetting the value of $SECONDS to 0 (SECONDS=0), you can restart the timer and measure a new interval from that point onward.

Note that $SECONDS is an integer variable, and it represents the number of seconds as a whole number. It does not include milliseconds or fractions of a second.

Therefore

1. Whenever you start a shell (for example, you open a graphical terminal window like Gnome-Terminal) a $SECONDS variable is assigned to it.
2. A $SECONDS variable is also assigned to the non-interactive shell that executes the bash noscript file.

https://preview.redd.it/9hpvk7qxy6zc1.png?width=732&format=png&auto=webp&s=67619f0a8a6cd077dcab79f4625490e406394c06

In the short video below, I have shown how to use the $@ and $SECONDS variables to send a command to a bash file and calculate its execution time.

# Watch videos on YouTube

**Send and execute a command to a noscript and calculate the execution time**

https://redd.it/1cn2g5u
@r_bash

Modify the bash prompt to indicate that the user is logged in with SSH

# Detecting that the current user is logged in with SSH?

To detect if the current user is logged in via SSH, you can check the value of the `SSH_CLIENT` environment variable. If the variable is set, it indicates that the user has logged in using SSH.
In this noscript, we use the `-n` test condition to check if the `SSH_CLIENT` variable is not empty. If it has a value, it means the user is connected via SSH, and the noscript outputs "You are logged in via SSH." Otherwise, it outputs "You are not logged in via SSH."

#!/bin/bash

if [[ -n "$SSH_CLIENT" ]]; then
echo "You are logged in via SSH."
else
echo "You are not logged in via SSH."
fi

In addition to the `SSH_CLIENT` environment variable, you can also check for the presence of other environment variables to determine if a user is logged in via SSH. Here are a few commonly used variables:

1. `SSH_CONNECTION`: This variable contains the client IP address, client port, server IP address, and server port in the format `client_ip client_port server_ip server_port`. If the variable is set, it indicates an SSH connection.
2. `SSH_TTY`: This variable is set if the user is logged in via SSH and is connected to a terminal. It holds the path to the TTY (terminal) device associated with the SSH session.
3. `SSH_AUTH_SOCK`: This variable is set when an SSH agent is running and available for authentication. Its presence indicates that the user has logged in via SSH and has access to an SSH agent.

Here's an example noscript that checks these variables to determine if the user is logged in via SSH:

#!/bin/bash

if [[ -n "$SSH_CLIENT" || -n "$SSH_CONNECTION" || -n "$SSH_TTY" || -n "$SSH_AUTH_SOCK" ]]; then
echo "You are logged in via SSH."
else
echo "You are not logged in via SSH."
fi

By checking the presence of any of these variables, the noscript can identify if the user is logged in via SSH. If any of the variables are set, it will output "You are logged in via SSH." Otherwise, it will output "You are not logged in via SSH."

Here's an example of how the `SSH_CONNECTION` environment variable would typically look if a user is logged in via SSH:

echo $SSH_CONNECTION
92.168.1.100 12345 203.0.113.10 22

* [`192.168.1.100`](http://192.168.1.100) is the client's IP address.
* `12345` is the client's port number.
* [`203.0.113.10`](http://203.0.113.10) is the server's IP address.
* `22` is the server's SSH port number.

The values are separated by spaces, and they represent the client's IP address, client's port, server's IP address, and server's port, respectively.

# Modify Bash Prompt

[Sample output](https://preview.redd.it/pt4xi3c2c9zc1.png?width=504&format=png&auto=webp&s=d9d416467d81bc74fd0c0ee671b8602085e62e23)

How to modify the prompt to indicate that the user is logged in via SSH: [**Watch videos on YouTube**](https://youtu.be/H0U5fJykTBg)

https://redd.it/1cndoho
@r_bash

How to delete duplicate #s in a line within file

Within all lines containing the words "CONECT", I need to remove duplicate #s
Ex:

CONECT 1 2 13 14 15
CONECT 2 1 3 3 7

CONECT 3 2 2 4 16

CONECT 4 3 5 5 17


Should be

CONECT 1 2 13 14 15

CONECT 2 1 3 7

CONECT 3 2 4 16

CONECT 4 3 5 17

Is there a way to do this using sed or awk?

https://redd.it/1cnf7yt
@r_bash

Window manager startup noscript isn't working

I'm not sure if this is the right place to post this, but I'm having an issue with my startup noscript and since it's written in bash (and the WM doesn't have a Subreddit), I figured I'd start here.

I'm trying to start a locker noscript within a WM startup noscript and, for whatever reason, everything else in my noscript starts except the locker.

Here's the relevant part in my WM file:

#!/usr/bin/env bash

...

dunst &
pidof -q picom || { picom & }
pidof -q pipewire || { pipewire & }
pidof -q syncthing || { syncthing & }
pidof -q redshift || { redshift & }

$HOME/noscripts/locker.sh 2>&1 || tee -a /tmp/locker.log & disown

And here's locker.sh:

#!/usr/bin/env bash

# Only exported variables can be used within the timer's command.
export PRIMARYDISPLAY="$(xrandr | awk '/ primary/{print $1}')"
export BRIGHTNESS="$(xbacklight -get)"

# Run xidlehook
xidlehook \
--not-when-fullscreen \
--not-when-audio \
--timer 300 \
"xbacklight -d $PRIMARYDISPLAY = 10 -time 1000" \
"xbacklight -d $PRIMARYDISPLAY = $BRIGHTNESS" \
--timer 30 \
"xbacklight -d $PRIMARYDISPLAY = $BRIGHTNESS; betterlockscreen -l dim" \
"" \
--timer 300 \
standby \
""

I'm not sure what's going on, and I've tried so many things. When I run `locker.sh` in my terminal, it works fine, so I'm pretty confused.

P.S. I'm using the DK window manager, which is similar to BSPWM, and my system is running Void Linux.

https://redd.it/1cnf0kh
@r_bash

Keeping the ID of the background processes and checking the status of their execution or termination

When you put & at the end of a command, the command is executed in the background. Variable $! In bash, it holds the ID of the last background process. My question is, how can we every time a process runs in the background, with the help of the variable $! Save the ID of that process and then check if it is still running or not.

https://redd.it/1cny4gr
@r_bash

Advice ragarding an archinstall bash noscript

Hello. For my school project I'm trying to make automate archinstall. the ArchLinux community has helped me with a great explination that I need to make a '.bash\_profile' file in the USB that I want to perform this in. However the issue itself is the noscript.

Someone wrote me an example noscript with what it could look like and with additonal help from gpt-4 I was able to get this noscript

#!/bin/bash

# Define the configuration settings in a variable
CONFIG='{
"keyboard-layout": "us",
"timezone": "Europe/Amsterdam",
"locale": "en_US.UTF-8",
"additional-packages": ["vim", "firefox", "gnome", "gnome-extra"],
"network": {
"hostname": "myarchsystem",
"interfaces": [
{
"interface": "eth0",
"dhcp": true
}
]
},
"users": [
{
"username": "FILL_IN",
"password": "FILL_IN",
"is-superuser": true
}
],
"harddrive": {
"path": "/dev/sda",
"layout": "default",
"filesystem": "ext4"
},
"bootloader": {
"install": true
},
"post-install": [
"systemctl enable gdm.service",
"systemctl enable NetworkManager.service"
]
}'

# Save the configuration to a file
echo "$CONFIG" > archinstall-config.json

# Check if the configuration file has been created and start archinstall
if [ -f "archinstall-config.json" ]; then
echo "Starting automated Arch Linux installation with GNOME..."
sudo archinstall --config "archinstall-config.json"
else
echo "Failed to create configuration file. Exiting."
exit 1
fi


A helpful user from this sub adviced me to use ShellCheck before with a different idea. ShellCheck says that this noscript is fine. Is this a good starting point?

The ArchLinux community's version of the bash noscript looks like this which is way different from what ChatGPT came up with.

#!/bin/bash

set -e
echo "g
n
p
1

+512M
n
p
2


w" | fdisk $1
mkfs.ext4 ${1}2
mkfs.vfat -F ${1}1
mount ${1}2 /mnt
mkdir /mnt/boot
mount ${1}1 /mnt/boot
pacstrap /mnt base base-devel linux linux-firmware
genfstab -U /mnt >> /mnt/etc/fstab
arch-chroot /mnt /bin/bash <<EOF
pacman -S --noconfirm grub
ln -sf /usr/share/zoneinfo/Sweden/Stockholm /etc/localtime
hwclock --systohc
locale-gen
echo "LANG=en_US.UTF-8" > /etc/locale.conf
echo "KEYMAP=sv-latin1" > /etc/vconsole.conf
echo "Manifestation" > /etc/hostname

systemctl enable dhcpcd@eth0.service
grub-install --target=x86_64-efi --efi-directory=/boot/grub --bootloader-id=84C55
grub-mkconfig -o /boot/grub/grub.cfg

EOF
echo -e "\e[91mDont forget to set passwd\e[0m"
echo -e "additionally use \e[91mumount -R /mnt\e[0m"



https://redd.it/1cnylv2
@r_bash