joplin-notes/joplin notion extension/linux/Basics.md

Basics https://linuxcommandlibrary.com/

• https://www.howtogeek.com/269509/how-to-run-two-or-more-terminal-commands-at-once-in-linux/
   
  Option One: The Semicolon (;) Operator
  The semicolon (;) operator allows you to execute multiple commands in succession, regardless of whether each previous command succeeds. For example, open a Terminal window (Ctrl+Alt+T in Ubuntu and Linux Mint). Then, type the following three commands on one line, separated by semicolons, and press Enter. This will give you a listing of the current directory
   
  Option Two: The Logical AND Operator (&&)
  If you want the second command to only run if the first command is successful, separate the commands with the logical AND operator, which is two ampersands ( && ). For example, we want to make a directory called MyFolder and then change to that directory--provided it was successfully created. So, we type the following on the command line and press Enter.
   
  Option Three: The Logical OR Operator (||)
  Sometimes you might want to execute a second command only if the first command does not succeed. To do this, we use the logical OR operator, or two vertical bars ( || ). For example, we want to check to see if the MyFolder directory exists ( [ -d ~/MyFolder ] ) and create it if it doesn't ( mkdir ~/MyFolder ). So, we type the following command at the prompt and press Enter.

• bash cheatsheet

  A; B    # Run A and then B, regardless of success of A
    A && B  # Run B if and only if A succeeded
    A || B  # Run B if and only if A failed
    A &     # Run A in background.
    A & B & : # Run A in background, then run B in background (regardless of success) and return control to the shell
  

• locating commands or bin files
  which -a gdb

  which: no gdb in (/home/hpm/.local/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl:/var/lib/snapd/snap/bin)
  
  

  rt
  locate -eb '\gdb'

  ed

  /usr/share/gdb
  /usr/share/bash-completion/completions/gdb
  /usr/share/glib-2.0/gdb
  /usr/share/gstreamer-1.0/gdb 
  

 

• sed commands usage
  https://www.tecmint.com/linux-sed-command-tips-tricks/ https://www.geeksforgeeks.org/sed-command-in-linux-unix-with-examples/

  Sed Command in Linux_Unix with examples - GeeksforGeeks.pdf

• List files with full path with ls
  ls -lrt -d -1 "$PWD"/{*,.*}
  or if u want regular expression then
  find /path/to/start/directory -type f | awk -F/ '{print "<a href=\""$0"\">"$NF"</a>"}'
  here path to directory is path where those files are stored
  type -f means to list only files
  find /path/to/start/directory -maxdepth 1 -type f -exec sh -c 'echo "<a href=\"{}\">$(basename {})</a>"' \; : this maxdepth flag can be used to list files only in current directroy and not go any deeper in those subdirectories

• cp command to copy folder contents along with hidden files use the period(.) symbol too cp -ar assets/. backup/ a is for archive means preserving metadata to copy files while excluding a file or directory rsync -av --progress sourcefolder /destinationfolder --exclude thefoldertoexclude --exclude anotherFolderToExclude Note : files to be excluded should be relative to source directory not the current directory from where this command is executed.

• Changing file name based on pattern

  for file in tomp3.cc*; do mv "$file" "${file/tomp3.cc - /}"
  done
  

• replacing names through like removing spaces for f in *\ *; do mv "$f" "${f// /_}"; done Though it's not recursive, it's quite fast and simple. I'm sure someone here could update it to be recursive. The ${f// /_} part utilizes bash's parameter expansion mechanism to replace a pattern within a parameter with supplied string. The relevant syntax is ${parameter/pattern/string}. See: https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html or http://wiki.bash-hackers.org/syntax/pe .

• sort file names on basis of names

  • ascending order ls *.jpg | sort -n
  • descending order ls *.jpg | sort -nr

• get ip address ip addr or ifconfig

• cat command

  1. cat notes.txt : to show contents of notes,txt
  2. > this will represent the transfer of data from left to right. If left side is empty then transfer from stdin to the file. All content of file will be replaced with stdin or whatever file on left.

  cat > notes.txt
  > hey there
  >^C
  > cat notes.txt
  > hey there
  

  3. >> will append data from left to right instead of truncaing it

  cat >> notes.txt
  > hey there
  >^C
  > cat >> notes.txt
  > how r you
  >^C
  > cat notes.txt
  > hey there
  > how r you
  

• aliases and function

  1. Functions

   function packagelist {
  dpkg -l | grep "$1" | awk '{print $2}' | tr "\n" " "
  } 
  packagelist gcc
  

  Output:

  

• Docs Install tldr package to get nicer docs. or tealdeer which is rust based

• Some utilties info tty is the terminal device a process is connected to it can be a physical terminal or a pseudo terminal ps is a command that displays process information and tail prints to output the last contents of a file by default the last 10 lines

ps -eo user= | sort | uniq -c one-liner counts the number of processes per user on the system ps -eo user= extracts only usernames with no header line (the '=' clears the custom header, which suppresses the header line entirely), sort arranges them, uniq -c counts processes per user. Without '=', the header row 'USER' itself would be counted as one entry.

• Check memory info free -m

• Check battery status To list devices upower -e Find battery one and get the result upower -i /org/freedesktop/UPower/devices/battery_BAT0

• Check desktop manager systemctl list-units | grep dm.service

  • Check whether xorg or wayland display server echo $XDG_SESSION_TYPE

• last argument access For eg if u have used mkdir test Then $_ will represent test So cd $_ = cd test

• for checking CPU architecture use uname -m

• zswap compresses ram istead of using storage space

• search for packages : pinned find /usr -name '*mingw*'

• script for mounting multiple partitions

    #!/bin/bash
  
    name1="mint"
    name2="manjaro"
    name3="hdd"
    name4="ssd"
  
  
    # Define partitions and mount points
    partition1="/dev/sda5" # mint
    partition2="/dev/sda6"  # manjaro
    partition3="/dev/sda3" # hdd
    partition4="/dev/nvme0n1p3" # ssd
    mount_point1="/mnt/$name1"
    mount_point2="/mnt/$name2"
    mount_point3="/mnt/$name3"
    mount_point4="/mnt/$name4"
  
    # Check if partitions are not mounted
    if ! mountpoint -q "$mount_point1"; then
    	mkdir -p /mnt/$name1
    	# Mount partition1
    	sudo mount "$partition1" "$mount_point1"
    	echo "Mounted $partition1 at $mount_point1"
    fi
  
    if ! mountpoint -q "$mount_point2"; then
    	mkdir -p /mnt/$name2
    	# Mount partition2
    	sudo mount "$partition2" "$mount_point2"
    	echo "Mounted $partition2 at $mount_point2"
    fi
  
    if ! mountpoint -q "$mount_point3"; then
    	mkdir -p /mnt/$name3
    	# Mount partition3
    	sudo mount "$partition3" "$mount_point3"
    	echo "Mounted $partition3 at $mount_point3"
    fi
  
    if ! mountpoint -q "$mount_point4"; then
    	mkdir -p /mnt/$name4
    	# Mount partition4
    	sudo mount "$partition4" "$mount_point4"
    	echo "Mounted $partition4 at $mount_point4"
    fi
  
  

• size of folders and files The du command in Linux is a powerful utility that allows users to analyze and report on disk usage within directories and files. The basic syntax of the du command is as follows:   du [options] [directory/file] eg : du -sh dir_name

• copy all files to next folder with exlcuding some directories say src rsync -av --exclude='src' . ~/cache_bkp . here is source and ~/cache_bkp is destination

• to prepend text // this way is working echo -e "your text to prepend\n$(cat sample.txt)" > sample.txt for large files

  echo "your text to prepend" > temp.txt
  cat sample.txt >> temp.txt
  mv temp.txt sample.txt
  

// below way isnt working cat - stringToBePrepended | tee -a sample.txt. cat - reads from standard input (in this case, the stringToBePrepended). Step 2: Pipes the output of cat - text.txt to the next command. Step 3: tee -a sample.txt tee -a appends the input to the sample.txt file. The -a option tells tee to append to the file instead of overwriting it. Overall effect: The cat - text.txt | tee -a sample.txt command reads the contents of text.txt, appends them to sample.txt, and also outputs them to the terminal. This effectively prepends the contents of text.txt to sample.txt. Harsh Truth — Today at 12:20 AM  

• Looping thorugh all arguments in bash

    for arg in "$@"; do
  	echo "arg: $arg"
    done
  

• Detecting flags in bash

  #!/bin/bash
  
    # Loop through all the arguments
    for arg in "$@"; do
      case $arg in
    	-a|--optionA)
    	  echo "Option A detected!"
    	  # handle option A
    	  ;;
    	-b|--optionB)
    	  echo "Option B detected!"
    	  # handle option B
    	  ;;
    	*)
    	  # Handle positional arguments or invalid flags
    	  ;;
      esac
    done
  

• sed sed -i 's/\(<string>\)\.md/\1/' your_file.txt This command captures the <string> before .md using parentheses and then replaces the entire match (including .md) with just <string>, effectively removing the .md extension when it follows <string>.
• Copy multiple files to a directory cp -t path/to/destination_directory path/to/file1 path/to/file2 ...
• Copy multiple directories to a directory(copy dir1 dir2 to targetDir) cp -r dir1 dir2 targetDir/
• Move multiple directories to directory mv -t path/to/destination_directory path/to/file1 path/to/file2 ...
• Login to different user sudo su - <user_name> and exit to exit
• User management https://www.freecodecamp.org/news/how-to-manage-users-in-linux/

  • Adding user useradd -u 1002 -d /home/john -s /bin/bash john or useradd -u 1002 -d /home/john -s /bin/bash john -g johnGroup -c comments

  • Getting user names Users and their other informatio separated by colons can be accessed by cat /etc/passwd To get only users awk -F: '{ print $1}' /etc/passwd Get users which can be logined getent passwd {1000..60000} 1000 is min UID and 60000 is max UID. They may be different so find them using grep -E '^UID_MIN|^UID_MAX' /etc/login.defs following for users with uid and gid cut -d: -f1-4 /etc/passwd

  • Getting group names cat /etc/group or cut -d: -f1 /etc/group | sort (for readable form)

    • get group names for a user groups $USER id $USER

  • Password setup After creatiing user before login in we can setup password by sudo passwd john

  • Adding permissions By default when user is created he dont have permission to write anything there so he cant create any directory or file too in his own home directory. Before login in type this sudo chown test:test /home/test

  • Adding user to group https://serverfault.com/questions/688685/usermod-ag-vs-gpasswd-a-as-a-best-practice sudo gpasswd -a $USER groupname or sudo usermod -aG groupname username or for adding user to multiple groups sudo usermod -aG additional_groups username additional_groups : comma separated list of groups

  • Ensure group changes to take effect newgrp group_name

  • Allowing user to use sudo Uncomment the line starring $ sudo ... then sudo usermod -aG sudo username so add user to sudo group -aG means adding user to group or use sudo usermod -aG wheel username if u dont wanna uncomment sudo and use wheel instead wheel will grant user priviledge to use sudo command To remove users from group 'wheel' sudo gpasswd -d username wheel

  • Changing ownership chown -c john file.txt (for users) or chown -c :johnGroup file.txt (for groups) -c for reporting for directories use chown -R -c john file.txt (for users)

  • Running command as different user without login su - username -c 'command' or sudo -u username command

  • Granting permissions to all root access priviledges to the user then add this to sudoers file (location : /etc/sudoers) username ALL=(ALL:ALL) ALL (very dangerous config so avoid it as much as possible as it will grant nlimited access too) when installing distro first user can use cd or ls command in directories without use of sudo so do this sudo usermod -aG autologin $USER to add ability as same of first user if it doesnt work then check permissions and using chmod change

  • Extended partition. access grant of directory can be drwxr-x--x+ here + at end stands for extended permissions means other user cant access its directories even if is set x permission in others. Extended permissions is honored by fish shell but not bash shell may not honor it. to change it use setfactl and to get its detail use getfactl To add extended permissions use setfacl -R u:user2:wrx /tmp to remove setfacl -bn /tmp

  • to check permissions of directory simply instead of all files in it use ls -ld <dirpath>

• For searching files find /home/user/ | grep filenamehere
• launch other user files with this sudo -e /path/to/other/users/binary -e preserves your current user's environment variables etc. so audio should work
• change to new user sudo su - test
• for searching files with particular extension also listing their meta data find . -type f -name "*.ess" -exec ls -l {} +
• for searching with min length 1 mb find -size +1M
• scrolling in terminal TIL that u can scroll in terminal with SHIFT+PGUP/PGDOWN
• useful commands to count number of files in current directory

   ls | wc -l
  

• tar and cpio cpio

  # creating archive of text files to archive.cpio
  find *.txt | cpio -o > archive.cpio 
  
  # extracting content to current directory
  cpio -i  < ../archive.cpio
  

• to search for content recurseively across all files in a directory grep -r hello <directory_path>
• resources, basic command video https://youtu.be/QhvDvpyvPSE

  Nick, tell the beginners use 'trash' instead of 'delete, to retain file availability.
    Nick, tell the beginners that 'pwd' is NOT password.
    Nick, tell the beginners that 'cd -' takes them between recent directories.
    Nick, tell the beginners that Windows says 'folders', but Linux says 'directories'.
    Nick, tell the beginners that uppercase and lowercase letters denote DIFFERENT things in Linux.
  

• arp -a to get list of all otheer ip address of systems connected to same network
• find number of files and directories recursively in given directory find . -type f | wc -l for files find . -type d | wc -l for directories  
• to identify distro u r using cat /etc/os-release
• to see disk space left for each partitions df -h  

for resumable downloads use -c in wget wget -c https://example.com