My Notes on Linux, Bash, whatsoever

Permissions

ID

The id command will provide information about current user.
Output: uid=1000(heiko) gid=1000(heiko) groups=1000(heiko),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),114(lpadmin),134(sambashare),136(docker)
uid = User Id
gid = primary Group Id
User acoounts are defined in the /etc/passwd file and groups in /etc/group.
Those files also defining accounts for superusers (uid 0) and other system users.
/etc/group holds the user's password information.
In older Unix-like systems users where assigned to a common group like "users", modern Linux practice is to create a unique single-member group with the same name as the user.

Reading, Writing, Executing

ls- l will show a list of files whiting a directoy with attributes like this: -rw-rw-r--
The first charakter (in my system not - but .) is the file type.

Attribute	File Type
- (.)	A regular file.
d	A directory
l	A symbolic link*
c	A character special file**
b	A block special file***

*a symbolic link will always show rwxrwxrwx --> those are dummy values, the real attributes are those of the file where the link points to.
**Device that handles data as a stream of bytes, such as a terminal or /dev/null
***Handles data in blocks, such as a hard drive or a DVD drive.

The remaining nine characters of the file attributes are called the file mode.
They represent read, write and execute permissions for the file's owner, group and everybody else (world).

Owner	Group	World
rwx	rwx	rwx

Attribute	Files	Directories
r	open, read	content can be listed if x is also set.
w	write, truncate, *	create, delete, rename files within directory
x	makes file executable**	allows to enter directory

*r attribute on file does not grand rename or delete, those permissions come from directory permissione
**must be readable also to be executed.

chmod - Change File Mode

chmod command is used to change file or directory permissions. It can be used only by the file's owner or a superuser.
chmod supports octal number or symbolic representation.

The Octal number system can be used to change permissions.

Octal	Binary	File Mode
0	000	---
1	001	--x
2	010	-w-
3	011	-wx
4	100	r--
5	101	r-x
6	110	rw-
7	111	rwx

Most common used: 7(rwx), 6(rw-), 5(r-x), 4(r--) and 0(---).
By passing three octa arguments to chmod, we are able to set owner, group and world permissions at once.
chmod 600 foo.txt; ls -l foo.txt will show -rw------- – read and write for the owner.
chmod 777 foo.txt; ls -l foo.txt will show -rwxrwxrwx – read, write and execute for the owner, the group and the world.

chmod also supports symbolic notation

Symbol	Meaning	Examples
u	user	`chmod u+x script.sh #Add execute permission for owner` `chmod u-x script.sh #Remove execute permission from owner`
g	group	`chmod u+rw,go=r file #read,write for owner, read only for group and others`
o	others (world)	`chmod go=r script.sh #this will set read for group and others – if they had write and execute before, it will be removed`
a	all (u+g+o)	`chmod +x script.sh #this will make script executable for all as "a+x" would`

umask

umask holds the default permission setting for new created files.
umask the command without any options will show the current default setting.
umask uses octals, but works kind of reverse as chmod. For a binary 1 in the octal table it takes the permission from the default settings.
umask 7777 would result in a default created file --------- while umask 0000 would grant rwxrwxrwx by default.
The whole thing works actually with only three digits, but the book states four would be more correct. I don't care at this point.

chown

chown changes the owner, the group or both of a file.
chown bob text.txt changes the owner of the text file to "bob".
chown bob:users text.txt changes the owner to "bob" and the group to "users".
chown :admins text.txt changes the group to "admins", owner remains unchanged.
chown bob: text.txt changes the owner to "bob" and the group to bob's login group.
In older Unix versions a separate command chgrp was used to change group ownership.

passwd

To change your password, just enter passwd into the shell.
A superuser can change passwords for others passwd bob.
The passwd command has options like setting an expiration date, etc. … can be found in the man page.

PROCESSES

Process Monitoring

The ps command

ps will show you basic information on running processes associated whit the current terminal session.
ps x | less will show us all of our processes regardless of what terminal they are controlled by.
This will lead in an outcome like this:

    PID TTY      STAT   TIME COMMAND
   1805 ?        Ss     0:00 /lib/systemd/systemd --user

STAT reveals the current status of a process:

State	Meaning
R	Running – process is running or ready to run
S	Sleeping – process not running; it is rather waiting for an event, such as a keystroke or network packet
D	Uninterruptible sleep – process is waiting for I/O such as a disk drive
T	Stopped – process has been instructed to stop
Z	Zombie – child process that was stopped but not yet cleaned up by parent
<	High Priority – process with more CPU time granted
N	Low Priority – process will get processor time after other processes have been serviced

The process state may be followed by ther characters. Check ps man page for more detailed process characteristics.

ps aux displays the processes belonging to every user.
Note: Using the options without a leading dash invokes the command with "BSD style".

Header	Meaning
USER	User ID of the process owner
%CPU	CPU usage in percent
%MEM	Memory
VSZ	Virtual memory size
RSS	Resident set size*
START	Time when the process started

*Amount of physical memory (RAM) used by the process (in kilobytes)

pstree will show a visualisation of running processes.
ps aux | grep bluethooth would also provide information on running "bluethooth" processes.
pgrep -li bluetooth pgrep is kind of a combined form of ps and grep, but it provides less information.
While the ps command can reveal a lot about what the machine is doing, it provides only a snapshot of the machine's state at the moment it is executed.
vmstat outputs a snapshot of system resource usage.

Viewing processed dynamically with top

top ist the terminal equivalent of System Monitoring and provides a detailed insight of running processes.
top | grep bluethooth will show all running processes containing the word "bluethooth" and keeps on refreshing changes on it.
The top command displays continuosly udating (3 sec by default) the running processes in order of process activity.

htop is a more detailed top-like monitoring tool.

To end top or htop press q.

Controlling Processes

There is a bunch of processes that can be used for testing purposes:
xlogo – sample program supplied with the X Window System (underlying graphic engine).
xeyes – this program is showing eyes following the mouse pointer.
glxgears – is a very basic graphics benchmark tool.

If a process like xlogo runs in the foreground, it can be interrupted with CTRL + c.
CTRL + z will send the process to the background.
The fg command can be used to bring that process back to foreground, bg to resume its execution in the background.
pidof xlogo will display ID(s) of running xlogo processes.

Killing Processes

kill 14349 will kill the process with the corresponding ID.
pkill xlogo will end all xlogo processes.
kilall xlogo will also end all xlogo processes.

Shutting down the system

sudo reboot, sudo halt, sudo poweroff may be used to halt, power-off, or reboot the machine. All three commands take the same options.
shutdown may also be used to halt, power-off or reboot the machine.
sudo shutdown -H now to --halt, sudo shutdown -P now to --poweroff, sudo shutdown -r now to --reeboot
The time string may either be in the format "hh:mm" for hour/minutes specifying the time to execute the shutdown at, specified in 24h clock format. Alternatively it may be in the syntax "+m" referring to the specified number of minutes m from now. "now" is an alias for "+0", i.e. for triggering an immediate shutdown. If no time argument is specified, "+1" is implied.

BASH

commands / receipies

cd                         # takes you back into the home  directory
cd -                       # takes you back into the last directory
cd ..                      # takes you one  director up

pwd                        # print working directory

realpath Mastering_Vim_Quickly_v1.1.pdf
# prints full path of the file "Mastering_Vim_Quickly_v1.1.pdf":
/home/heiko/books/mastering_vim/book/Mastering_Vim_Quickly_v1.1.pdf

mv 8ball eightball         # renames the file 8ball to eightball within same directory
mv eightball somedir/      # moves the eightball file to the somedir directory
# IMPORTANT: Get into the habbit to always use a / when moving a file into a directory!
# This will save you from accidentally overwriting a file with an similar name.
# An other good habbit to prevent this is to use tab completion -> which always puts a / behind directories.
  
df                         # shows free disk space
dg -h                      # shows it in human readable format

free -h                    # shows available memory in human readable format

chmod +x hello             # makes the hello file executable
exec bash                  # refreshes bash 

which ls                   # will show you if / where the ls command is /bin/ls installed
type ls                    # will show if ls has been overwritten by alias
                           # use \ to execute the actual command --> \ls
# IMPORTANT: which will still show you the original command directory, even if the command was overwritten.
# Always use the type command if you want to know what exactly will be running.

ls test1/ test2/           # will list files of test1 and test 2 directory
ls -lt                     # will show list in long format last modified first   
ls -lt --reverse           # will show list in long format first modified first   

cp -u *.html test1/        # will copy all .html files to test1 directory
                           ## which do not exist in test1 already or 
                           ### which do exist there in an older version
cp -a * test1/             # will copy all files and directories with all attributes (ownership, permissions) to the test1 dir.
cp -r test1/ test2/        # will recursively copy test1 and its content to test2. -r or -a are required when copying directories.
cp ~/test1/*.html ~/test2  # will copy all .html files from test1 to test2 directory
cp ~/test1/* ~/test2       # will copy all files from test1 to test2 directory
cp -i test.txt test1/      # will copy test.txt to the test1 directory and ask for confirmation to overwrite, if a text.txt file already exists in there.
# IMPORTANT: note that cp without the -i option will silently replace identically named files!

rm -r test1/ test2/        # will remove test1 and test 2 directory + all files included files
rm *.html                  # will remove all .html files in working directory
# IMPORTANT: Be careful with the rm command as it will delete files permanently.
# A minor typo while using wildcards could have a huge impact.
# The above command rm *.html with an extra space rm * .html would delete all files within the directory.
# Use the wildcard with ls command first to ensure the outcome is as expected, then replace ls with rm. 

file TLCL-19.01.pdf        # Provides information on a file (TLCL-19.01.pdf: PDF document, version 1.5). 

ln file1 file2             # will create a hard link between file1 and file2
                           # whenever one file is changed, the other will change too
                           # when one file will be removed, the other will remain keeping the content
                           # file two will have no visible indicator that it is a link
                           # the number behind permissions in long list will indicate how many instances of the file exists (-rw-rw-r--  2)
                           # all instances will change when one gets edited
ln -s file1 file2          # will create a symbolic link between file1 and file2
                           # a visible indicator will show the connection in a list (file2 -> file1)
                           # when one file is edited, file1 will contain the change, file2 will only display it.
                           # when file1 is removed, file2 will be broken and not contain any content.
                           # when file2 gets deleted file1 remains unchanged
                            
apropos copy               # will search al man pages for the term "copy" and list the results.
whatis ls                  # will show a one-line description of what the "ls" command does
whatis $(ls /usr/bin) | grep -v "nothing appropriate" | less
# this command substitution will show the whatis entry of all programms in /user/bin and cut out empty entries.

pstree                     # shows running processes as a tree.

##### FIND ##### REDIRECT #####
find / -name '*.md'                                            #find
# finds all files ending with ".md" + error for files without permissions

find / -name '*.md' 2>/dev/null                                #find #redirect
# to exclude the error messages use the following command:

find / -name '*.md' 2>/dev/null 1>/tmp/found                   #find #redirect
# find all files with ".md" in the name, send errors to dev/null*, save result in found file in tmp directory.

find / -name '*.md' &>/tmp/found                               #find #redirect
# &> will redirect results + errors to the specified file. 

echo "1st line in file" > aa1                                  #redirect #create #overwrite
# will write "1st line in file" into the first line of the "aa1" file.
# the file will be created if it doesn't exist
# IMPORTANT: if the file exist > will overwrite the file - no matter what it contained before, it will only contain one line "1st line in file" then.
# To prevent > from overwriting files, place "set -o noclobber" in your .bashrc.
# With noclober set, an error occures when you try to > an existing file.
# use >| to overwrite a file when #noclober is set

> aa1                                                          #redirect #empty 
# This would completely empty the "aa1" file, but keep the empty file. 

echo "some text" >> aa1                                        #redirect #append 
# >> would append the string "some text" to the next empty line in the "aa1" file.

# *dev/null is the nirvana of the shell. It is also called "bit bucket" or "black hole". 
# https://en.wikipedia.org/wiki/Null_device

##### APT #####
sudo apt update
# refreshes the index of what packages are available at which version

sudo apt install tmux -y
# will install tmux and automatically answer **yes** to questions like additional disk space due to the **-y** option 

sudo apt install tmux htop git
# will install three application at once

sudo apt remove zathura -y
# will remove the app zathura without further questions

sudo apt search vim
# will show all available vim packages like vim-nox, neovim, etc.

sudo apt upgrade
# updates all packages with updates available 
# make sure index is up-to-date (sudo apt update) before you upgrade

sudo apt dist-upgrade
# performs upgrades for apps which require the previous removal or installation of a package

sudo vim /etc/apt/sources.list
# will open the sources file for apt

##### CAT #####
cat notes.txt
# This would display the content of "notes.txt" in the terminal.
# The cat command is mostly used to display short texts in standard output.

cat movie.mkv.0* > movie.mkv 
# If a file is split into multiple parts, cat can be used to combine them together.

cat
# If you type cat without a command or file, it will wait for standard input.
# CTRL + d will tell cat that the files end has been reached and cat will send what was typed to standard output.

cat > notes.txt
# This behavior can be used to generate textfiles with cat.
# New words / lines can be entered directly into the terminal.
# When CTRL + d get's pressed, all the input is commited to the file.

cat >> notes.txt
# Text can as well be appended to a file this way.

##### PIPELINES ##### SORT ##### LESS ##### UNIQ ##### WC ##### GREP #####
# Pipelines (|) take the output of one command and hand it over to another.

ls /bin /usr/bin | sort | less
# lists all files in bin + usr/bin, sorts them and displays the output terminal window by window.
# Without sort, the output would be two sorted lists 2x a-z after each other, so it is 1x a-z.

ls /bin /usr/bin | sort | uniq | less 
# uniq removes any dublicates from the sorted list, so that every entry only exists once.

ls /bin /usr/bin | sort | uniq -d | less
# the -d option of the uniq command can be used to display only the dublicate values from a list.

ls /bin /usr/bin | sort | uniq -d | wc -l
# adding the wc (word count) command with the -l option would display the number of dublicates

wc notes.txt
# The wc command without options will show the number of lines, word and bytes of a file.

ls /bin /usr/bin | sort | uniq | grep zip
# The grep command will reduce the output to only those lines which contain the word "zip".
# The -v option would show only lines NOT containing "zip".
# Use the -i option to ignore case sensetivity.

ls /bin /usr/bin | sort | uniq | grep -v zip | head -n 5
ls /bin /usr/bin | sort | uniq | grep -v zip | tail -n 5
# The head command would will show only the first 5, the tail command only the last 5 lines of our output.
# The default lines shown for both commands is 10 but any desired number can be specified after the -n option.
# I've detected that is works also without -n (head -5).

tail -f logfile
# The tail command has the option -f which coninues to monitor changes to the end of the file.
# This is especially usefull to monitor logfiles. It can be exited with CTRL + c.
# Article on advanced tail usage: https://www.howtogeek.com/481766/how-to-use-the-tail-command-on-linux/

ls /bin /usr/bin | sort | uniq -d | tee complete_list | grep zip
# The "tee" command allows to save an intermediate result to a file and continue with the pipe.
# In this example it saves the sorted unique output to "complete_list" before the list gets reduced to only those lines which contains "zip".

### git -> connecting to gitlab
ssh git@gitlab.com         # will show you if your ssh key is set up correctly or not

git config --global user.name heiko__c #set username in config file
git config --global user.email heiko.kraemer@protonmail.com #set email in config file
git config -l #shows config entries
git init 
git remote add origin git@gitlab.com:heiko__b/eightball
git add .
git commit -m "initial commit"
git push -u origin master

### default editor
sudo update-alternatives --config editor

Wildcards / Expansion

Wildcard	Meaning
*	Matches any characters
?	Matches any single character
[characters]	Matches any character that is a member of the set characters
[!characters]	Matches any character that is not a member of the set characters
[[:class:]]	Matches any character that is a member of the specified class

Character Class	Meaning
[[:alnum:]]	Matches any alphanumeric character
[[:alpha:]]	Matches any alphabetic character
[[:digit:]]	Matches any numeral
[[:lower:]]	Matches any lowercase letter
[[:upper:]]	Matches any uppercase letter

Wildcard Examples	What it does
`rm *.jpg`	will remove all JPGs in working directory
`cp sys*.txt logfiles/`	will copy all textfiles beginning with "sys" to logfile directory
`rm *data????`	will remove all files with "data" before four other characters (newdata.txt, mydata.jpg)
`rm [dD]*`	will remove all files beginning with "D" or "d"
`rm BACKUP.[0-9][0-9][0-9]`	will remove all files beginning with "BACKUP" followed by three numerals
`ls 1*[Tt]`	will list all files beginning with "1" and ending with "T" or "t"
`ls [[:upper:]][a-z][a-z][a-z].txt`	will list 4-letter textfiles beginning with an upper case
`ls [A-Z][a-z][a-z][a-z].txt`	will show exactly the same result as the one above
`ls [![:digit:]]*`	will list files not beginning with numerals
`ls *[[:lower:]123]`	will list files ending with a lower case or the number "1", "2" or "3"
`ls {day,night}`	will list all files containing day or night
`ls !([Tt][Ee][Ss][Tt])`	will list all files not containing "test", "Test", "TEST", tEsT, …
`ls [Tt][Ee][Ss][Tt]!([0-9])`	will list files starting with "test" (case insensitive) not ending with numeral
`echo .[!.]*`	will display all dotfiles but not ".."
`echo [!AaBb]*`	will display all non-dotfiles not starting with A,a,B,b
`echo !(Desktop	Documents
`rm test{1..5}`	will remove "test1", "test2", "test3", "test4" and "test5"
`ls -{FRA1,FRA2}-`	will list all files containing -FRA1- or -FRA2-, like test-FRA1-777, test-FRA2-775
`mkdir {1981..2021}-{01..12}`	will create 12 directories for each year from 1981 to 2021 in the format 1981-01

Extensive Wildcard Examples

ls [![:digit:]]*[0-9][0-9][0-9]*[![:digit:]]
This will list all files containing (at least) three numerals but not beginning or ending with one.
File examples: test1234test test123test test123Test tesT123test

ls [![:digit:]]*[a-z][0-9][0-9][0-9][aA-zZ]*[![:digit:]]
This will only list files which are

containing exactly 3 digits
a lower case letter before those digits
an upper case letter after those digits
do not start or end with numerals

File examples: test123test test123Test

touch FRA1-{A{001..12},B{013..24}}-Port
This will create files "FRA1-A001-Port" - "FRA1-A012-Port" and "FRA1-B013-Port" - "FRA1-B024-Port".

Related term globbing:
In shell-speak, globbing is what the shell does when you use a wildcard in a command (e.g. * or ?). Globbing is matching the wildcard pattern and returning the file and directory names that match and then replacing the wildcard pattern in the command with the matched items.

Bash scripting

watch ./greet will repetitive (every 2 sec) execute the "greet" script and let you watch.
while true; do ./greet; sleep 2; clear; done will do the same.
Both methods can be used to live-view what changes to your script will do on its output.

echo "${color}Hello ${reset}${name}"      #echo requires -n option not to do a line break.
printf "${color}Hello ${reset}${name}\n"  #with printf a linebreak has to be set (\n)

Conditionals

Simple IF Statement

read -p "Enter your name " NAME

if [ "$NAME" == "Brad" ]
  then
  echo "Yoyoyoy Brad!"
else
  echo "Hello $NAME"
fi

Declare condition in square brackets. The shown example asks user for input – his/her name –, if the name is Brad, a specialised greeting will be shown. All other names will be greeted with "Hello".

ELSE-IF (elif)

if [ "$NAME" == "Brad" ]
  then
  echo "Yo Brad, whaaazzzup!!??"
elif [ "$NAME" == "Heiko" ]
  then
  echo "Hey Heiko, you're the best man!"
else
  echo "Hello $NAME"
fi

Same behavior here with Brad, but here's a second name "Heiko" which has an other special greeting defined.

Comparison

NUM1=3
NUM2=5

if [ "$NUM1" -gt "$NUM2" ]
  then
  echo "$NUM1 is greater than $NUM2"
else
  echo "$NUM1 is less than $NUM2"
fi

-gt stands for greater than. Output: 3 is less than 5

NUM1=3
NUM2=5

if [ "$NUM1" -ne "$NUM2" ]
  then
  echo "$NUM1 is not equal to $NUM2"
else
  echo "$NUM1 is equal to $NUM2"
fi

-ne stands for not equal. Output: 3 is not equal to 5

-eq stands for equal
-ge stands for greater than or equal
-lt stands for less than
-le stands for less than or equal

File Conditions

FILE="text.txt"

if [ -f "$FILE" ]
  then
  echo "$FILE is a file"
elif [ -d "$FILE" ]
  then
  echo "$FILE is a directory"
else
  echo "$FILE is neither a file nor a directory"
fi

-f true if file. -d true if directory. Output: text.txt is a file

-e true if file exists
-g true if group id is set on file
-r true if file is readable
-s true if file has non-zero size
-u true if user id is set on file
-w true if file is writable
-x true if file is executable

Case Statement

read -p "Are you 21 or over? " ANSWER

case "$ANSWER" in
  [yY] | [yY][eE][sS])
    echo "You can have a beer :)"
    ;;
  [nN] | [nN][oO])
    echo "Sorry, no drinking (in the US)"
    ;;
  *)
    echo "Please enter y/yes or n/no"
    ;;
esac

The script above takes user input and handels it with case. IMPORTANT: Closing bracket required after specified case (no opening brackets). Double semicolon after specified command! esac to mark the end of case.

Simple FOR Loop

NAMES="Brad Kevin Alice Mark"

for NAME in $NAMES
  do
    echo "Hello $NAME" | lolcat
    sleep 0.5
done

FOR Loop to rename files

clear
rm \*demo
touch abc.demo def.demo ghi.demo jkl.demo mno.demo pqr.demo stu.demo vwx.demo yzz.demo

FILES=$(ls \*.demo)
DATE=$(date -I)

echo "Adding Date"
sleep 1

for FILE in $FILES
    do
      echo "Renaming $FILE to $DATE-$FILE" | lolcat
      mv $FILE $DATE-$FILE
      sleep 1
done
sleep 1

FILES=$(ls \*.demo)

echo "Removing Date"
sleep 1

for FILE in $FILES
    do
      FILENAME=$FILE
      echo "Renaming $FILE to ${FILENAME:11}" | lolcat
      mv $FILE ${FILENAME:11}
      sleep 1
done
sleep 3

This little demo script creates demo files, renames it by adding the current date upfront and reverse that change by cutting away the date again. All for the sake of demo, lolcat is totally optional.
Stars escaped because of issues with the markdown - does backslash should be removed before running the script.

WHILE Loop – Read through a file line by line

LINE=1

while read -r CURRENT_LINE
  do
    echo "$LINE: $CURRENT_LINE"
    ((LINE++))
    sleep 5
done < "./der_spieler"

Script reads through Dostojewski's "Der Spieler" and prints it line by line on the screen.
The line number is shown, the LINE variable increments with each iteration.

if [ "$1" == "read" ] ; then
LINE=1
while read -r CURRENT_LINE
  do
    echo "$LINE: $CURRENT_LINE" 
    ((LINE++))
    sleep 5
done < "./der_spieler"
else
  echo "tell me what to do!"
fi

The same script within an if statement if [ "$1" == "read" ] would only read those lines from the book, when the called it with the read optin. ./myscript.sh read.
If called without an option (or with any other option) the scrip would return "tell me what to do!".

Testing

#!/bin/bash -x as long as -x is behing the bash declaration, the script will print out additional information on what commands are running when executed.
test $a == "b" && echo "Yep" || echo "Nope" would test if the variable "a" is equal to the value "b" – and if true echo "Yep", if false echo "Nope".
&& is used to execute an other command after the prior command run successfully.
|| is used to execute an other command after the prior command did not run successfully.

Creating a log file for your script

To create a log file for any script, the first thing would be to check if there is an existing log file.
In this example we are going to create a log file for a script myscript whiting a prior created logfiles directory.

if [ ! -f /home/$USER/logfiles/myscript.log ]; then
  echo "┌( ಠ_ಠ)┘ logfile -- myscript --" \
  > /home/$USER/logfiles/myscript.log 
fi

log file tbc

Install missing package quietly

dpkg -l | grep -qw git || sudo apt-get install -yyq git
This series of commands would check if the "git" package is already installed -> and if not install it without the requirement of further input by the user.
Super useful method to install a set of default tools on a new system.

Where to put a script

You'll want to move your script to someplace within your path statement so you can run it like any other installed program on your system. There are two preferred places for scripts and compiled programs not handled by your distro's package manager:

/home/username/bin
or
/usr/local/bin

Many distros will detect when you create a bin directory in your home directory and add it to path statement automatically (handled by .profile or .bashrc).

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/bin" ] ; then
    PATH="$HOME/bin:$PATH"
fi

# set PATH so it includes user's private bin if it exists
if [ -d "$HOME/.local/bin" ] ; then
    PATH="$HOME/.local/bin:$PATH"

Misc

You can break down a long line into more readable parts by usind the backslash charakter \.
echo $'\n' something will echo "something" with a blank line above it.

Here document

cat << _EOF_
Endlich bin ich nach vierzehntägiger Abwesenheit zurückgekehrt. Die Unsrigen befinden sich schon seit drei Tagen in Roulettenburg. Ich hatte geglaubt, sie warteten bereits auf mich mit der größten Ungeduld; indes ist dies meinerseits ein Irrtum gewesen. Der General zeigte eine sehr stolze, selbstbewußte Miene, sprach mit mir ein paar Worte sehr von oben herab und schickte mich dann zu seiner Schwester. Offenbar waren sie auf irgendwelche Weise zu Geld gekommen. Es kam mir sogar so vor, als sei es dem General einigermaßen peinlich, mich anzusehen. Marja Filippowna hatte außerordentlich viel zu tun und redete nur flüchtig mit mir; das Geld nahm sie aber in Empfang, …
_EOF_

The use of the EOF tag (or any other) print that text on the screen while keeping its format and without the requirement to exit any signes user in bash, like quotes, etc.

sudo apt install xclip jq vim rofi snapd git neofetch cargo ranger brave \
htop locate lynx tmux postman keepassxc vs code nmap docker.io whois \
beep lolcat

The above shown example would be interpreted as only one line.

Parameter expansion

name=World
echo "Hello ${name}"

no matter what the input is … World, WORLD, world, wOrLd or whatever, you can specify the format of the output like this:

${name,,} will show as world.
${name^^} will show as WORLD.

echo ${var} #Output: tak3 this simple t3xt #prints var

echo ${#var} #Output: 21 #shows length of var (including spaces)

echo ${var:0} #Output: tak3 this simple t3xt #shows everything from letter zero to end

echo ${var:2} #Output: k3 this simple t3xt #shows var after letter two

echo ${var:0:2} #Output: ta #shows var from letter zwero to letter two

echo ${var:0:-2} #Output: tak3 this simple t3 #shows var from letter zero to end minus two

echo ${var:4:-4} #Output: this simple #shows var after letter four to end minus four

echo ${var: -4} #Output: t3xt #shows minus four letters from end (space required!)

echo ${var/s/z} #Output: tak3 thiz simple t3xt

replaces first appearance of "s" in var with "z"

echo ${var//s/z} #Output: tak3 thiz zimple t3xt in var #replaces all "s" in var with "z"

echo ${var//this/that} #Output: tak3 that simple t3xt #replaces all "this" in var with "that"

echo ${var:0:-5}_abc #Output: tak3 this simple_abc #cuts last five letters, adds "_abc"


### Command substitution
`echo "Today is $(date)"` will print: "Today is Mon 11 Jan 2021 12:44:17 PM CET". <br>
`echo one plus one is $((1 + 1))` will print: "one plus one is 2". <br>
*math substitutions require a second set of brackets to be calculated* <br>

```bash
declare -i quater=3
echo "Result: $((100 / 12 * quater))"

Outcome of this is: "Result: 24"
math substitutions are the only place that do nor require a "$" to use a variable.

Working with Parameters and Arguments

Parameter: Slot, a thing where you can put something in.
Argument: The thing that goes in the paramenter.
General wisdom: When in doubt, quote it out So if you're not sure, if you require something in double quotes to functure properly .. put those quotes around it!
So let's say our script greet contains the following:

declare name="$1"
echo "Hello ${name}"

It will take the first argument and place it into the variable "name".
greet World will result in the output Hello World.

declare name="$1"
declare name="${1:-World}"

This sets a default output to "World" .. if called greet Heiko, the output will be Hello Heiko if called greet it will be Hello World.

Globstar

Globstar allows to search recursively through sub-directories.
It has to be enabled for a script of generally via the bashrc.
The command to enable it is shopt -s globstar.

Example: ls -a **test* will show you all files containing test in the current directory + it's sub-directories.

Quoting

There are two types of quoting:
Weak: uses double quotes: "
Strong: use single quotes: '

If you want to bash to expand your argument, you can use Weak Quoting:

#!/usr/bin/env bash
world="World"
echo "Hello $world"
#> Hello World

If you don't want to bash to expand your argument, you can use Strong Quoting:

#!/usr/bin/env bash
world="World"
echo 'Hello $world'
#> Hello $world

You can also use escape to prevent expansion:

#!/usr/bin/env bash
world="World"
echo "Hello \$world"
#> Hello $world

Source: https://riptutorial.com/bash

NETWORKING

The ping command sends packages to a specified host and provides information on package travel speed.
Example: ping heikokraemer.de provides information regarding the connection to the server where heikokraemer.de is hosted.
The tracepath command provides informations about the hops to the specified target.
nslookup (from name server lookup) is a network administration command-line tool for querying the Domain Name System (DNS) to obtain domain name or IP address mapping, or other DNS records.
dig is a command-line tool for querying DNS name servers for information about host addresses, mail exchanges, name servers, and related information. It supersedes in functionality older tools, such as nslookup.
ip -br a shows the connections your computer hast to the internet.
127.0.0.1 or lokalhost - is the hostname that refers to the current computer. https://en.wikipedia.org/wiki/Localhost
vi /etc/services shows a list of all service ports.
The scp command copies files over a secure, encrypted network connection. https://www.computerhope.com/unix/scp.htm

SSH

Create ssh key: ssh-keygen -t ed25519 Note: we have used the -t option to specify key type ed25519.
ATTENTION: processing like this is ok to generate the very first ed25519, but carefull not to overwrite an existing key – it could be your only way to enter a server.
ssh-keygen -t ed25519 -C "pihole" the -C option can be used to comment on the key's usage.
In the next steps the ssh-keygen is asking Enter file in which to save the key – it is as above mentioned really important to change the default file name if multiple keys exist, the first key gets silently overwritten otherwise!
A password for the key is optional, but recommended – especially when using it with an employeer or client. Everyone with access to an unsecured key would be able to identify as yourself and log into all remote systems using the key. A missing pw could even have legal consequences.
Find your own naming convention, if you're for example using the key dedicated for a pihole dns server, name it pihole_id_ed25519.
ssh-add ~/.ssh/pihole_id_ed25519 can be used to store a private key in memory for the running ssh agent session – that way you'll have to entere the pw only once for that session.

Show public key: cat .ssh/id_ed25519.pub
Login into something: ssh root@167.71.42.169
Copy something over: scp /home/heiko/.bashrc root@167.71.42.169:

Place the following information into ~/.ssh/config to establish a connection by addressing the host: ssh bboost

Host bboost
        User root
        Hostname 167.71.42.169
        IdentityFile ~/.ssh/id_ed25519.pub

ssh bboost 'ls -alht' > bboost-home will perform a list command within the home directory of the remote host "bboost" and save its output in as file "bboost-home" within the working directory.
Use single quotes to hand over commands to a remote machine.
ssh user@host "$(declare -f upgr);upgr" will execute the local "upgr" function on the remote system.
Use double quotes to declare and execute functions.
ssh-copy-id -i ~/.ssh/id_ed25519.pub root@167.71.42.169 can be used to copy the public key over to a remote system.

sshd (ssh daemon)

systemctl status sshd shows the sshd status.
The sshd_config lives in the /etc/ssh directory.
Warning: dont's delete any of those host key files in that directory or you won't be able to re-connect to the server!
sshd_config is important to change the default port, root login permit, password authentications, etc.
service ssh restart or systemctl restart sshd restarts sshd (required to load sshd_config changes).
Important: don't disconnect from the remote system until you've tested the sshd config change in an other session!

PermitRootLogin should be set to no – !!after!! an other login user has been created. This is an important security setting as root is a powerful default admin user which all hackers are going to use. Shutting down that default setting is shutting down default attacks.

PasswordAuthentication should been set to no as soon as ssh has been setup has been completed.

Tracking user logins

You can track user login login sessions with tail -f /var/log/auth.log.

Troubleshooting ssh

timeout messages could mean that the port is blocked by the router/firewall.
permissions should be checked
- ssh will only work if the private keys are rw by the user and nothing more.
- the .ssh/ directory should only be rwx by your user
- same on the remot side, .ssh/ and authorized key files should only be rw by you
if you have a user with issues loging in .. let him try while you tail the logs

User Management

To naviagate a system as root user is dangerous, because that user can change and delete everything. So any mistake could have irretrievable consequences .. loss of data, etc.
There are two command to create a new user useradd and adduser.
adduser is a perl script which leads as a single command through the whole user creation process, while useradd requires to manually execute a series of commands.

adduser hk will create a new user hk.
One way to give that user the rights to use the sudo command and therewith to install software, etc. is to edit the group file in the etc directory.
vim /etc/group --> and then add the username at the and of the sudo line: sudo:x:27:hk
To eneable ssh login for that user ..
su - hk (logged in as root -> login as hk)
mkdir .ssh (create .ssh directory)
chmod 700 .ssh (make directory only readable for that user)
vim authorized_keys -> paste outcome from cat .ssh/id_ed25519.pub on local host into that file and save.
Now change the ~/.ssh/config to User hk -> ssh bboost will now log you in as hk.

Host bboost
        User hk
        Hostname 167.71.42.169
        IdentityFile ~/.ssh/id_ed25519.pub

To change default port on host:

vim /etc/ssh/sshd_config
# then change "Port" to 29999
service sshd restart
# add port setting to ssh config or use command:
ssh -p 29999 root@jitsi.myforce.net

Searching for files

locate

locate performs rapid database searchs of pathnames and outputs every name matching the given substring.
locate bin/zip would provide us a list with all programs starting with "zip".
There are several variants of locate – most common are slocate and mocate.
locate won't work at a fresh installation or most recent files as it's using a search databes updated by a cron job.
That cron job is running updatedb which can as well be run at the promt by the superuser.
Looks like Raspian has no locate installed by default.

find

find is an other search command and it comes with a lot of interesting features.
find ~ | wc -l will find and count all files in home + all sub-directories.

-type

find ~ -type d | wc -l will count the directories starting from home.
find ~ -type f | wc -l will count the regular files starting from home.

file type	descriptio
b	Block special device file
c	Charakter special device file
d	Directory
f	Regular fiel
l	Symbolic link

-name pattern

find ~ -type f -name ".vim*" will show all vim dotfiles.
-name can be used with the wildcard pattern:
find ~ -name '[A-Z][a-z][a-z][a-z].txt' will find all 4-letter .txt files starting with a capital letter, like Test.txt or Find.txt.
find ~ -name '*[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]*' finds all files containing a date structure like 2019-04-23.

-size n

find ~ -type f -name "*.png" -size +500k will show all png files larger than 500kbyte
-size + searchs for files larger … - for files lower than the specified unit.

Size Units:

Character	Unit
b	512-byte blocks (default if not specified)
c	Bytes
w	2-byte words
k	Kilobytes
M	Megabytes
G	Gigabytes

NOTE

-cmin / -ctime vs. -mmin / -mtime
c: means that either the content was changed, or the file's metadata (permission, owner, etc).
m: means that only the content was modified.

-cmin n

$ find ~ -type f -cmin -5 finds files which were changed less then 5 minutes ago.
$ find ~ -type f -cmin +5 finds files which were changed more then 5 minutes ago.
$ find ~ -type f -cmin 5 finds files which were changed exactly 5 minutes ago.

-cnewer n

find ~ -type f -cnewer ~/.bashrc finds files modified after .bashrc was las modified.
-cnewer requires full path: find ~ -type f -cnewer ~/repos/gitlab.com/heiko__b/dotfiles/notes.md

-ctime n

find ~ -type d -ctime 2 shows directories whose contents or metadata were modified within th last two hours.

-empty

find ~ -type d -empty shows all empty directories.

-group name

find ~ -type f -group heiko | wc -l shows all files belonging to group heiko.

-iname pattern

Like name but case-insensitive
find ~ -type d -iname "*music*" shows all directories whose name contains music or Music, etc.

-mmin n

find ~ -mmin -10 | wc -l counts files whose contents were changed less then ten minutes ago.

-mtime n

find ~ -type d -ctime 2 shows directories whose contents were modified within the last two hours.

-newer file

like -cnewer but only for datachanges, does not compare metadata changes like permissions.

-nouser

find ~ -nouser | wc -l finds files not belonging to a valid user.
Can be used to find belongings of deleted accounts or detect activity by attackers.

-nogroup

find ~ -nogroup | wc -l finds files not belonging to a valid group.

-perm mode

find ~ -perm 777 | wc -l counts files and directories that are rwxrwxrwx.

-user name

find ~ -user heiko | wc -l counts all files and directories belonging to user heiko.

logical operators (-and, -or, -not)

Multiple find options can be combined usind logical operators:
find ~ $ -type f -not -perm 0600 $ -or $ -type d -not -perm 0700 $

predefined find actions

Action	Description
-delete	Delete the current matching file
-ls	Equivalent of `ls -dils`
-print	Outputs full path of matching files (default)
-quit	Quit once a match has been made

`find ~ -type f -name '*.xyz1' -delete` will find and delete all files ending with .xyz1.
#### user defined *find* actions All kind of commands can be used with the matching files / directories by usind:
`-exec command '{}' ';'` or `-ok command '{}' ';'`
**-exec** performs the action immediately: `find ~ -type f -name '*.xyz1' -exec rm '{}' ';'`
*All files ending on .xyz1 will be removed after executing that command.*
**-ok** performy the action file by file after user confirmation: `find ~ -type f -name '*.xyz1' -ok rm '{}' ';'`
That command will result in a dialog `< rm ... /home/heiko/test1/def.xyz1 > ?` which has to be confirmed with **y** or declined with **n** for each file.
**Note**: those commands above will execute their actions per files – which in most cases is an unnecessary heavy use of resources.
So instead of ending our *remove* example with **';'** the following command will execute it on all files combined:
`find ~ -type f -name '*.xyz1' -exec rm '{}' +` **+** will rm *file1* *file2* …

#### xargs An other way to execute such actions more efficient is the `xargs` command.
**xargs** constructs and argument list of the prior output and executes a specified command:
`find ~ -type f -name '*.xyz1' | xargs rm` is the xargs version of our *remove* example

options

Option	Description
-depth	Process a directory's files before itself
-maxdepth levels	Set max depth directory tree level
-mindepth levels	Set min depth directory tree level
-mount	Do not traverse on other file systems mounted directories
-noleaf	No Unix-like search optimization (needed for CD-ROMs / Windows file systems)

Options must be placed before any other arguments
find -depth -name '*xyz*' -exec rm -r '{}' + without -depth the system would delete first findings first – so if a directory would be named xyz and countain files named xyz, an error would be throw when the system tries to delte files it had already deleted with the directory.

Licenses for free software

Apache License V2 https://www.apache.org/licenses/LICENSE-2.0.html
Creative Commons https://creativecommons.org/choose/
GNU General Public License https://en.wikipedia.org/wiki/GNU_General_Public_License

further reaserch

tab completion (Linux Beginner Boost Day 3 - 41:00)
Rob's .vimrc & .bashrc -> for PLATFORM (linux,windows,mac,unknown)
- check out how he sets different behaviours based on the platform he's working on.
rwxrob's vim plugins and outoload plugin manager. Left that out my vimrc for now.
wemux
cd path withing rob's dotfiles (bashrc).
I've skipped signals .. it's at page 144 in the book.
Wargames: https://overthewire.org/wargames/bandit/ Bandit to chapter 5.
Setup a Linux Server on all the major cloud providers
- AWS, Google, Azure, Digital Ocean, Linode, Hetzner
- Connect two of those servers together
curl http://ix.io/2mD6 | cat read through all those settings from Rob's .bashrc
checkout and fully understand pstree - what it is, what it does, what it shows
Know difference between desktop- display- and window-manager
Check out "Browsersync"
Check out ip and netstat command in detail to gain more networking skills
Learn more about ftp, lftp, wget and how to use it securely for filesharing
Learn more about systemctl command

Turorials, resources

https://subsignal.org/doc/AliensBashTutorial.html List of tutorials: https://riptutorial.com/bash/awesome-learning/tutorial Terminal commands sorted by topics: http://www.linuxguide.it/command_line/linux_commands_en.html

Misc

rwxrob's random comments

don't use aliases -> use functions!
- aliases can't be used by scripts
export: makes a function available to child processes
- export -f greet to export "greet" -f = function
- && export -f greet after the greet function ensures that the function gets exported – only if there is no error in it.
$1: variable for the first input
$*: will allow the input to contain spaces
create the file first, with touch, not via the editor
- that way you'll realise no write access on dir before editing

MUTT

Mutt is a terminal email client.

installation & configuration

sudo apt-get install mutt get's mutt installed.
Create file ~/.config/mutt/muttrc and write inside:

set folder ="imaps://mailadress@here.pl@Mailserver.information.here:993"

set spoolfile = "+INBOX"

Opening mutt or neomutt if installed will now ask you for the mail pw.
You can now browse and read through your email. N are new mails, r marks emails you have replied too.
? will show you all the key-bindings in place.
c then ? shows a list of all available mailboxes – should be none at this point.
So to set up some mailboxes and make the mail sendable the muttrc must be completed like this:

set folder = "imaps://mailadress@here.pl@Mailserver.information.here:993"
set smtp_url = "smtp://mailadress@here.pl@Mailserver.information.here:587"

set from = "mailadress@here.pl"
set realname = "Your Name"

set spoolfile = "+INBOX"
set record = "+Sent"
set trash = "+Trash"
set postponed = "+Drafts"

mailboxes =INBOX =Sent =Trash =Drafts =Junk

The entry of your mail-password will be required as set.

gpg

gpg or gpg2 come with basically every distro are used for basic encryption.

gpg --full-gen-key #this command will initialise the process to generate a key
                   #it will be followed by a series of options

## PATH
gpg: keybox '/home/heiko/.gnupg/pubring.kbx' created

## KEY TYPE
Please select what kind of key you want:
   (1) RSA and RSA (default)
   (2) DSA and Elgamal
   (3) DSA (sign only)
   (4) RSA (sign only)
  (14) Existing key from card
Your selection? 1

## KEY SIZE
RSA keys may be between 1024 and 4096 bits long.
What keysize do you want? (3072) 4096
Requested keysize is 4096 bits

##  EXPIRATION
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 0
Key does not expire at all
Is this correct? (y/N)

An identity name and email must be given and a password will be required to protect the key.
To encrypt a file, use: gpg -r your.mail@your-domain.com -e file
your.mail@your-domain.com should be the mail you specified as identifier.
file.gpg will be cerated – file will remain in the directory and has to be removed manually.
gpg -d file.gpg > file would decrypt file back in its former apperance.
The entry of the former set password will be required to decrypt file.gpg.

pass

sudo apt install pass to install pass.
pass init your.mail@your-domain.com* toinitialize a password storage.
pass add email will add the password email to your password storage.
pass or pass ls will list all stored passwords:

Password Store
└── email

pam-gnupg to unlock key-pair on login: https://github.com/cruegge/pam-gnupg

dmenu

sudo apt install dmenu to install dmenu.
man -k . | dmenu -l 30 will show a 30 lines visible list of all available manual files. As you type in your search the 30 lines will change to relevant output.
passmenu to show passwords and copy them to clipboard

zathura

sudo apt install zathura to install zathura.

virtualbox

Oracle® VirtualBox® User Manual
Reboot after install and add yourself to the vboxusers group.
Using vb is actually quite simple. This YouTube video gives a good overview.
I'm using some Mac OS applications which are kind of mandatory for me. So my first virtualbox project was to set up a virtual mac.
This tutorial to run a mac on virtualbox worked well for me.
The tutorial's script comes with a nice little otion menue and finalises the setup of the virtual mac:

#!/bin/bash

PS3='Please select the VM: '
n=0
while read line ; do
  options[n++]="$line"
done <<<"$(vboxmanage list vms | awk '{$NF=""; print $0}' | tr -d '"')"
select opt in "${options[@]}" ; do
  vm_name="$opt"
  break
done

echo "Running updates for \"${vm_name}\" VM"

vboxmanage modifyvm "$vm_name" --cpuidset 00000001 000106e5 00100800 0098e3fd bfebfbff && echo "Changed CPU ID Set" ; sleep .5
vboxmanage setextradata "$vm_name" "VBoxInternal/Devices/efi/0/Config/DmiSystemProduct" "iMac11,3" && echo "Changed DmiSystemProduct" ; sleep .5
vboxmanage setextradata "$vm_name" "VBoxInternal/Devices/efi/0/Config/DmiSystemVersion" "1.0" && echo "Changed DmiSystemVersion" ; sleep .5
vboxmanage setextradata "$vm_name" "VBoxInternal/Devices/efi/0/Config/DmiBoardProduct" "Iloveapple" && echo "Changed DmiBoardProduct" ; sleep .5
vboxmanage setextradata "$vm_name" "VBoxInternal/Devices/smc/0/Config/DeviceKey" "ourhardworkbythesewordsguardedpleasedontsteal(c)AppleComputerInc" && echo "Changed DeviceKey" ; sleep .5
vboxmanage setextradata "$vm_name" "VBoxInternal/Devices/smc/0/Config/GetKeyFromRealSMC" 1 && echo "Changed GetKeyFromRealSMC" ; sleep .5
vboxmanage setextradata "$vm_name" "VBoxInternal2/EfiGraphicsResolution" "2560x1440" && echo "Changed resolution to 2560x1440" ; sleep .5

commands can also be run individual, screen resolution should be adjusted

surfshark vpn

Download installer from surfshark.com
sudo apt-get install {/path/to/file} then sudo apt-get update and sudo apt-get install surfshark-vpn.
surfshark should be ready to go now, try sudo surfshark-vpn. You'll have to enter your credentials.
sudo surfshark-vpn help will show all available command. most important are:
sudo surfshark-vpn attack will connect you to the fastest available vpn server.
sudo surfshark-vpn status will show the connection status of your vpn.
sudo surfshark-vpn down will disconnect you from vpn service.
I have written two functions vpnc and vpnd to cannect/disconnect sufshark.
Those functions can be found in my bash config.
They are using the myip which I've – as I belive – stolen from rwxrob to show the old/new public ip.

lynx

lynx is a text based webrowser. To install lynx type sudo apt install lynx -y
. Check out the lynx config: vim /etc/lynx/lynx.cfg
It has close to 4000 lines and the official lynx user guide also ain't lean … those lynx folks are text-savy for sure.
Typing lynx opens a kind of offensive colored About Lynx page, not very inviting, but let's check it out.
There are atually two files in cd /etc/lynx/ lynx.cfg and lynx.lss.
config: sudo vim /etc/lynx/lynx.cfg colors: sudo vim /etc/lynx/lynx.lss.
Whatched rob's video on lynx and just copied his lynx.lss – much better colorscheme, it's readable now.

navigation in lynx

So by default the arrow keys are used to navigate.
down moves down/right, up moves up/left. The cursor jumps from link to link.
right to follow a link. left to go back to the last page.
h the lynx help is as rich and well documented as everything so far.
/ to search, q to quit.
By pressing q only 1x, lynx requires a confirmation to quit with y.
q q quits lynx without further confirmation required.
g will open a prompt to enter a URL whre to go next.
p will open the print menu – providing information about the file, such as Number of lines.
Print options are:

Save to a local file
Mail the file
Print to the screen
Print out to a printer

I'm actually not sure what that print to the screen option is for as the content is already on the screen.
m for main is actually quite useful. It doesn't bring you to the default start page which can be specified within lynx.cfg, but to the page where you've started to follow links.
delete is supposed to provide a history list, but it doesn't.
o the options menu is most interesting. Here you can change those settings which are also managed in lynx.cfg I guess.
I've managed to save my changes by checking Save options to disk and click left on Accept Changes.
Colors swapped back to the default after that, but it looks like my changes were saved.
I've activated vim keybindings and to auto-accept cookies.

vim keybindings have the disadvantage that you start entering jjjjjj and stuff as soon as you hit some entry field.
lynx https://github.com/HeikoKramer/linux/blob/main/linux_notes.md brings you to this file on github.com.
I'm used to edit this file in vim, so browsing it in lynx with that link to link navigation and other colors fiels weird.
But it is generally good readable. The search works kind of like in vim.
The changes made in the options menu where not saved to lynx.cfg – but to ~/.lynxrc
I have changed some settings in lynx.cfg too .. time will show if there is a conflict between that file and .lynxrc.
One thing I have not setup yet is the downloader -> starting at line 1752 in lynx.cfg.
I'd like to setup uGet here, but have to research / try how to do that correctly.
There is a COLOR_STYLE section at line 3019 in lynx.cfg. Looks like you can choose between six color styles there.
I'll leave the colors as copied from rob for now, but that section is worth to check out later.
There is an interesting selction ENABLE_LYNXRC starting at line 3398 in lynx.cfg.
There you can manage which changes via the option menue will be saveable to .lynxrc.
My guess is that .lynxrc can overwrite setting from lynx.cfg, but that is an assumption.

lynx functions

Inspired by rwxrob's duck and google functions (below), I've created two wiki functions.
wikie searches within the english … wikid within the german wikipedia.

# duck – takes user input and performs a duckduckgo search with it in the lynx browser
function duck {
  lynx "duckduckgo.com/lite?kd=-1&kp=-1&q=$*";
}

# google – takes user input and performs a google search with it in the lynx browser
function google {
  lynx "google.com/search?q=$*";
}

# wikie – takes user input and performs a search within the english wikipedia via lynx
function wikie {
  lynx "en.wikipedia.org/wiki/$*";
}

# wikid – takes user input and performs a search within the german wikipedia via lynx
function wikid {
  lynx "de.wikipedia.org/wiki/$*";
}

ansible

getting started with ansible – prerequisite ssh

Notes while following the LLTV ansible tutorial series
sudo apt install openssh-server on the remote client

Files

linux_notes.md

Latest commit

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linux_notes.md

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My Notes on Linux, Bash, whatsoever

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