| _config.yml | ||
| README.md | ||
Bash-Oneliner
Hi bash learners and bioinformaticans, welcome to Bash Oneliner. I started studying bioinformatics data three years ago (recently started working on cloud computing), and was amazed by those single-word bash commands which are much faster than my dull scripts, so i started bash. Not all the code here is oneliner (if the ';' counts..), but i put effort on making them brief and fast.
This blog will focus on simple bash commands for parsing data, most of which are for tsv files (tab-separated values); some of them are for Linux system maintaining. I apologize that there won't be any citation for the codes, but they are probably from dear Google and Stackoverflow.
English and bash are not my first language, so... correct me anytime, thank you
In case you would like to check and vote up my questions on Stackoverflow, here's my page: http://stackoverflow.com/users/4290753/once
Here's a more stylish version~ http://onceupon.github.io/Bash-Oneliner/
Handy Bash oneliner commands for tsv file editing
Grep
Extract text bewteen words (e.g. w1,w2)
grep -o -P '(?<=w1).*(?=w2)'
Grep lines without word (e.g. bbo)
grep -v bbo filename
Grep only one/first match (e.g. bbo)
grep -m 1 bbo filename
Grep and count (e.g. bbo)
grep -c bbo filename
Insensitive grep (e.g. bbo/BBO/Bbo)
grep -i "bbo" filename
Count occurrence (e.g. three times a line count three times)
grep -o bbo filename
COLOR the match (e.g. bbo)!
grep --color bbo filename
Grep search all files in a directory(e.g. bbo)
grep -R bbo /path/to/directory
or
grep -r bbo /path/to/directory
Search all files in directory, only output file names with matches(e.g. bbo)
grep -Rh bbo /path/to/directory
or
grep -rh bbo /path/to/directory
Grep OR (e.g. A or B or C or D)
grep 'A\|B\|C\|D'
Grep AND (e.g. A and B)
grep 'A.*B'
Grep all content of a fileA from fileB
grep -f fileA fileB
Grep a tab
grep $'\t'
Grep variable from variable
$echo "$long_str"|grep -q "$short_str"
if [ $? -eq 0 ]; then echo 'found'; fi
//grep -q will output 0 if match found
//remember to add space between []!
Grep strings between a bracket()
grep -oP '\(\K[^\)]+'
Grep number of characters with known strings in between(e.g. AAEL000001-RA)
grep -o -w "\w\{10\}\-R\w\{1\}"
// \w word character [0-9a-zA-Z_] \W not word character
A lot examples here
http://www.cyberciti.biz/faq/grep-regular-expressions/
Sed
Remove lines with word (e.g. bbo)
sed "/bbo/d" filename
Edit infile (edit and save)
sed -i "/bbo/d" filename
When using variable (e.g. $i), use double quotes " "
e.g. add >$i to the first line (to make a FASTA file)
sed "1i >$i"
//notice the double quotes! in other examples, you can use a single quote, but here, no way!
//'1i' means insert to first line
Delete empty lines
sed '/^\s*$/d'
or
sed 's/^$/d'
Delete last line
sed '$d'
Delete last character from end of file
sed -i '$ s/.$//' filename
Add string to end of file (e.g. "]")
sed '$s/$/]/' filename
Add newline to the end
sed '$a\'
Add string to beginning of every line (e.g. bbo)
sed -e 's/^/bbo/' file
Add string to end of each line (e.g. "}")
sed -e 's/$/\}\]/' filename
Add \n every nth character (e.g. every 4th character)
sed 's/.\{4\}/&\n/g'
Concatenate/combine/join files with a seperator and next line (e.g seperate by ",")
sed -s '$a,' *.json > all.json
Substitution (e.g. replace A by B)
sed 's/A/B/g' filename
Select lines start with string (e.g. bbo)
sed -n '/^@S/p'
Delete lines with string (e.g. bbo)
sed '/bbo/d' filename
Print every nth lines
sed -n '0~3p' filename
//catch 0: start; 3: step
Print every odd # lines
sed -n '1~2p'
Print every third line including the first line
sed -n '1p;0~3p'
Remove leading whitespace and tabs
sed -e 's/^[ \t]*//'
//notice a whitespace before '\t'!!
Remove only leading whitespace
sed 's/ *//'
//notice a whitespace before '*'!!
Remove ending commas
sed 's/,$//g'
Add a column to the end
sed "s/$/\t$i/"
//$i is the valuable you want to add
e.g. add the filename to every last column of the file
for i in $(ls);do sed -i "s/$/\t$i/" $i;done
Add extension of filename to last column
for i in T000086_1.02.n T000086_1.02.p;do sed "s/$/\t${i/*./}/" $i;done >T000086_1.02.np
Remove newline\ nextline
sed ':a;N;$!ba;s/\n//g'
Print a number of lines (e.g. line 10th to line 33 rd)
sed -n '10,33p' <filename
Change delimiter
sed 's=/=\\/=g'
Replace with wildcard (e.g A-1-e or A-2-e or A-3-e....)
sed 's/A-.*-e//g' filename
Remove last character of file
```bash`` sed '$ s/.$//'
##### Insert character at specified position of file (e.g. AAAAAA --> AAA#AAA)
```bash``
sed -r -e 's/^.{3}/&#/' file
Awk
Set tab as field separator
awk -F $'\t'
Output as tab separated (also as field separator)
awk -v OFS='\t'
Pass variable
a=bbo;b=obb;
awk -v a="$a" -v b="$b" "$1==a && $10=b' filename
Print line number and number of characters on each line
awk '{print NR,length($0);}' filename
Find number of columns
awk '{print NF}'
Reverse column order
awk '{print $2, $1}'
Check if there is a comma in a column (e.g. column $1)
awk '$1~/,/ {print}'
Split and do for loop
awk '{split($2, a,",");for (i in a) print $1"\t"a[i]} filename
Print all lines before nth occurence of a string (e.g stop print lines when bbo appears 7 times)
awk -v N=7 '{print}/bbo/&& --N<=0 {exit}'
Print filename and last line of all files in directory
ls|xargs -n1 -I file awk '{s=$0};END{print FILENAME,s}' file'
Add string to the beginning of a column (e.g add "chr" to column $3)
awk 'BEGIN{OFS="\t"}$3="chr"$3'
Remove lines with string (e.g. bbo)
awk '!/bbo/' file
Column subtraction
cat file| awk -F '\t' 'BEGIN {SUM=0}{SUM+=$3-$2}END{print SUM}'
Usage and meaning of NR and FNR
e.g.
fileA:
a
b
c
fileB:
d
e
awk 'print FILENAME, NR,FNR,$0}' fileA fileB
fileA 1 1 a
fileA 2 2 b
fileA 3 3 c
fileB 4 1 d
fileB 5 2 e
AND gate
e.g.
fileA:
1 0
2 1
3 1
4 0
fileB:
1 0
2 1
3 0
4 1
awk -v OFS='\t' 'NR=FNR{a[$1]=$2;next} NF {print $1,((a[$1]=$2)? $2:"0")}' fileA fileB
1 0
2 1
3 0
4 0
Round all numbers of file (e.g. 2 significant figure)
awk '{while (match($0, /[0-9]+\[0-9]+/)){
\printf "%s%.2f", substr($0,0,RSTART-1),substr($0,RSTART,RLENGTH)
\$0=substr($0, RSTART+RLENGTH)
\}
\print
\}'
Give number/index to every row
awk '{printf("%s\t%s\n",NR,$0)}'
Break combine column data into rows
e.g.
seperate
David cat,dog
into
David cat
David dog
detail here: http://stackoverflow.com/questions/33408762/bash-turning-single-comma-separated-column-into-multi-line-string
awk '{split($2,a,",");for(i in a)print $1"\t"a[i]}' file
Sum up a file (each line in file contains only one number)
awk '{s+=$1} END {print s}' filename
Average a file (each line in file contains only one number)
awk '{s+=$1}END{print s/NR}'
Print field start with string (e.g Linux)
awk '$1 ~ /^Linux/'
Sort a row (e.g. 1 40 35 12 23 --> 1 12 23 35 40)
awk ' {split( $0, a, "\t" ); asort( a ); for( i = 1; i <= length(a); i++ ) printf( "%s\t", a[i] ); printf( "\n" ); }'
Subtract previous row values (add column6 which equal to column4 minus last column5)
awk '{$6 = $4 - prev5; prev5 = $5; print;}'
Xargs
Set tab as delimiter (default:space)
xargs -d\t
Display 3 items per line
echo 1 2 3 4 5 6| xargs -n 3
//1 2 3
4 5 6
Prompt before execution
echo a b c |xargs -p -n 3
Print command along with output
xargs -t abcd
///bin/echo abcd
//abcd
With find and rm
find . -name "*.html"|xargs rm -rf
Delete fiels with whitespace in filename (e.g. "hello 2001")
find . -name "*.c" -print0|xargs -0 rm -rf
Show limits
xargs --show-limits
Move files to folder
find . -name "*.bak" -print 0|xargs -0 -I {} mv {} ~/old
or
find . -name "*.bak" -print 0|xargs -0 -I file mv file ~/old
Move first 100th files to a directory (e.g. d1)
ls |head -100|xargs -I {} mv {} d1
Parallel
time echo {1..5} |xargs -n 1 -P 5 sleep
a lot faster than
time echo {1..5} |xargs -n1 sleep
Copy all files from A to B
find /dir/to/A -type f -name "*.py" -print 0| xargs -0 -r -I file cp -v -p file --target-directory=/path/to/B
//v: verbose|
//p: keep detail (e.g. owner)
With sed
ls |xargs -n1 -I file sed -i '/^Pos/d' filename
Add the file name to the first line of file
ls |sed 's/.txt//g'|xargs -n1 -I file sed -i -e '1 i\>file\' file.txt
Count all files
ls |xargs -n1 wc -l
Turn output into a single line
ls -l| xargs
Count files within directories
echo mso{1..8}|xargs -n1 bash -c 'echo -n "$1:"; ls -la "$1"| grep -w 74 |wc -l' --
// "--" signals the end of options and display further option processing
Download dependencies files and install (e.g. requirements.txt)
cat requirements.txt| xargs -n1 sudo pip install
Count lines in all file, also count total lines
ls|xargs wc -l
Xargs and grep
cat grep_list |xargs -I{} grep {} filename
Find
List all sub directory/file in the current directory
find .
List all files under the current directory
find . -type f
List all directories under the current directory
find . -type d
Edit all files under current directory (e.g. replace 'www' with 'ww')
find . name '*.php' -exec sed -i 's/www/w/g' {} \;
if no subdirectory
replace "www" "w" -- *
//a space before *
Find and output only filename (e.g. "mso")
find mso*/ -name M* -printf "%f\n"
Find and delete file with size less than (e.g. 74 byte)
find . -name "*.mso" -size -74c -delete
//M for MB, etc
Loops
While loop, column subtraction of a file (e.g. a 3 columns file)
while read a b c; do echo $(($c-$b));done < <(head filename)
//there is a space between the two '<'s
While loop, sum up column subtraction
i=0; while read a b c; do ((i+=$c-$b)); echo $i; done < <(head filename)
If loop
if (($j==$u+2))
//(( )) use for arithmetic operation
if [[$age >21]]
Test if file exist
if [ -e 'filename' ]
then
echo -e "file exists!"
fi
For loop
for i in $(ls); do echo file $i;done
Download
Download all from a page
wget -r -l1 -H -t1 -nd -N -np -A mp3 -e robots=off http://example.com
//-r: recursive and download all links on page
//-l1: only one level link
//-H: span host, visit other hosts
//-t1: numbers of retries
//-nd: don't make new directories, download to here
//-N: turn on timestamp
//-nd: no parent
//-A: type (seperate by ,)
//-e robots=off: ignore the robots.txt file which stop wget from crashing the site, sorry example.com
Upload a file to web and download (https://transfer.sh/)
--> upload:
curl --upload-file ./filename.txt https://transfer.sh/filename.txt
(the above command will return a URL, e.g: https://transfer.sh/tG8rM/filename.txt)
--> download:
curl https://transfer.sh/tG8rM/filename.txt -o filename.txt
Download file if necessary
data=file.txt
url=http://www.example.com/$data
if [! -s $data];then
echo "downloading test data..."
wget $url
fi
Wget to a filename (when a long name)
wget -O filename "http://example.com"
Wget files to a folder
wget -P /path/to/directory "http://example.com"
Random
Random pick 100 lines from a file
shuf -n 100 filename
Random order (lucky draw)
for i in a b c d e; do echo $i; done| shuf
Echo series of random numbers between a range (e.g. shuffle numbers from 0-100, then pick 15 of them randomly)
shuf -i 0-100 -n 15
Echo a random number
echo $RANDOM
Random from 0-9
echo $((RANDOM % 10))
Random from 1-10
echo $(((RANDOM %10)+1))
Xwindow
X11 GUI applications! Here are some GUI tools for you if you get bored by the text-only environment.
Enable X11 forwarding,in order to use graphical application on servers
ssh -X user_name@ip_address
or setting through xhost
--> Install the following for Centos:
xorg-x11-xauth
xorg-x11-fonts-*
xorg-x11-utils
Little xwindow tools
xclock
xeyes
Open pictures/images from ssh server
1. ssh -X user_name@ip_address
2. apt-get install eog
3. eog picture.png
Use gedit on server (GUI editor)
1. ssh -X user_name@ip_address
2. apt-get install gedit
3. gedit filename.txt
Open PDF file from ssh server
1. ssh -X user_name@ip_address
2. apt-get install evince
3. evince filename.pdf
Use google-chrome browser from ssh server
1. ssh -X user_name@ip_address
2. apt-get install libxss1 libappindicator1 libindicator7
3. wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
4. sudo apt-get install -f
5. dpkg -i google-chrome*.deb
6. google-chrome
Others
Remove newline / nextline
tr --delete '\n' <input.txt >output.txt
Replace newline
tr '\n' ' ' <filename
To uppercase/lowercase
tr /a-z/ /A-Z/
Compare files (e.g. fileA, fileB)
diff fileA fileB
//a: added; d:delete; c:changed
or
sdiff fileA fileB
//side-to-side merge of file differences
Number a file (e.g. fileA)
nl fileA
or
nl -nrz fileA
//add leading zeros
Combine/ paste two files (e.g. fileA, fileB)
paste fileA fileB
//default tab seperated
Reverse string
echo 12345| rev
Read .gz file without extracting
zmore filename
or
zless filename
Run in background, output error file
some_commands &>log &
or
some_commands 2>log &
or
some_commands 2>&1| tee logfile
or
some_commands 2>&1 >>outfile
//0: standard input; 1: standard output; 2: standard error
Send mail
echo 'heres the content'| mail -A 'file.txt' -s 'mail.subject' me@gmail.com
//use -a flag to set send from (-a "From: some@mail.tld")
.xls to csv
xls2csv filename
Append to file (e.g. hihi)
echo 'hihi' >>filename
Make BEEP sound
speaker-test -t sine -f 1000 -l1
Set beep duration
(speaker-test -t sine -f 1000) & pid=$!;sleep 0.1s;kill -9 $pid
History edit/ delete
~/.bash_history
or
history -d [line_number]
Get last history/record filename
head !$
Clean screen
clear
or
Ctrl+l
Send data to last edited file
cat /directory/to/file
echo 100>!$
Run history number (e.g. 53)
!53
Run last command
!!
Run last command that began with (e.g. cat filename)
!cat
or
!c
//run cat filename again
Extract .xf
1.unxz filename.tar.xz
2.tar -xf filename.tar
Install python package
pip install packagename
Delete current bash command
Ctrl+U
or
Ctrl+C
or
Alt+Shift+#
//to make it to history
Add something to history (e.g. "addmetohistory")
#addmetodistory
//just add a "#" before~~
Sleep awhile or wait for a moment or schedule a job
sleep 5;echo hi
Count the time for executing a command
time echo hi
Backup with rsync
rsync -av filename filename.bak
rsync -av directory directory.bak
rsync -av --ignore_existing directory/ directory.bak
rsync -av --update directory directory.bak
rsync -av directory user@ip_address:/path/to/directory.bak
//skip files that are newer on receiver (i prefer this one!)
Make all directories at one time!
mkdir -p project/{lib/ext,bin,src,doc/{html,info,pdf},demo/stat}
//-p: make parent directory
//this will create project/doc/html/; project/doc/info; project/lib/ext ,etc
Run command only if another command returns zero exit status (well done)
cd tmp/ && tar xvf ~/a.tar
Run command only if another command returns non-zero exit status (not finish)
cd tmp/a/b/c ||mkdir -p tmp/a/b/c
Extract to a path
tar xvf -C /path/to/directory filename.gz
Use backslash "" to break long command
cd tmp/a/b/c \
> || \
>mkdir -p tmp/a/b/c
Get pwd
VAR=$PWD; cd ~; tar xvf -C $VAR file.tar
//PWD need to be capital letter
List file type of file (e.g. /tmp/)
file /tmp/
//tmp/: directory
Bash script
#!/bin/bash
file=${1#*.}
//remove string before a "."
file=${1%.*}
//remove string after a "."
Search from history
Ctrl+r
Python simple HTTP Server
python -m SimpleHTTPServer
Variables
{i/a/,}
e.g. replace all
{i//a/,}
//for variable i, replace all 'a' with a comma
Read user input
read input
echo $input
Generate sequence 1-10
seq 10
Sum up input list (e.g. seq 10)
seq 10|paste -sd+|bc
Find average of input list/file
i=`wc -l filename|cut -d ' ' -f1`; cat filename| echo "scale=2;(`paste -sd+`)/"$i|bc
Generate all combination (e.g. 1,2)
echo {1,2}{1,2}
//1 1, 1 2, 2 1, 2 2
Generate all combination (e.g. A,T,C,G)
set = {A,T,C,G}
group= 5
for ((i=0; i<$group; i++));do
repetition=$set$repetition;done
bash -c "echo "$repetition""
Read file content to variable
foo=$(<test1)
Echo size of variable
echo ${#foo}
Echo tab
echo -e ' \t '
Array
declare -A array=()
Send a directory
scp -r directoryname user@ip:/path/to/send
Split file into lines (e.g. 1000 lines/smallfile)
$ split -d -l 1000 bigfilename
Rename all files (e.g. remove ABC from all .gz files)
rename 's/ABC//' *.gz
Remove extention (e.g remove .gz from filename.gz)
basename filename.gz .gz
zcat filename.gz> $(basename filename.gz .gz).unpacked
Use the squeeze repeat option (e.g. /t/t --> /t)
tr -s "/t" < filename
Do not print nextline with echo
echo -e 'text here \c'
Use the last argument
!$
Check last exit code
echo $?
View first 50 characters of file
head -c 50 file
Group/combine rows into one row
e.g.
AAAA
BBBB
CCCC
DDDD
cat filename|paste - -
-->
AAAABBBB
CCCCDDDD
cat filename|paste - - - -
-->
AAAABBBBCCCCDDDD
Fastq to fasta
cat file.fastq | paste - - - - | sed 's/^@/>/g'| cut -f1-2 | tr '\t' '\n' >file.fa
Cut and get last column
cat file|rev | cut -d/ -f1 | rev
Add one to variable/increment a numeric variable (e.g. $var)
((var++))
Some handy environment variables
$0 :name of shell or shell script.
$1, $2, $3, ... :positional parameters.
$# :number of positional parameters.
$? :most recent foreground pipeline exit status.
$- :current options set for the shell.
:pid of the current shell (not subshell).
$! :is the PID of the most recent background command.
Clear the contents of a file (e.g. filename)
>filename
Unzip tar.bz2 file (e.g. file.tar.bz2)
tar xvfj file.tar.bz2
Output a y/n repeatedly until killed
'y':
yes
or 'n':
yes n
or 'anything':
yes anything
For example:
yes | rm -r large_directory
Create dummy file of certain size instantly (e.g. 200mb)
dd if=/dev/zero of=//dev/shm/200m bs=1024k count=200
Standard output:
200+0 records in
200+0 records out
209715200 bytes (210 MB) copied, 0.0955679 s, 2.2 GB/s
System
Snapshot of the current processes
ps
Check graphics card
lspci
Show IP address
$ip add show
or
ifconfig
Check system version
cat /etc/*-release
Linux Programmer's Manuel: hier- description of the filesystem hierarchy
man hier
List job
jobs -l
Export PATH
export PATH=$PATH:~/path/you/want
Make file execuable
chmod +x filename
//you can now ./filename to execute it
List screen
screen -d -r
Echo screen name
screen -ls
Check system (x86-64)
uname -i
Surf the net
links www.google.com
Add user, set passwd
useradd username
passwd username
Edit variable for bash, (e.g. displaying the whole path)
1. joe ~/.bash_profile
2. export PS1='\u@\h:\w\$'
//$PS1 is a variable that defines the makeup and style of the command prompt
3. source ~/.bash_profile
Edit environment setting (e.g. alias)
1. joe ~/.bash_profile
2. alias pd="pwd" //no more need to type that 'w'!
3. source ~/.bash_profile
List environment variables (e.g. PATH)
$echo $PATH
//list of directories separated by a colon
List all environment variables for current user
$env
Show partition format
lsblk
Soft link program to bin
ln -s /path/to/program /home/usr/bin
//must be the whole path to the program
Show hexadecimal view of data
hexdump -C filename.class
Jump to different node
rsh node_name
Check port (active internet connection)
netstat -tulpn
Find whick link to a file
readlink filename
Check where a command link to (e.g. python)
which python
List total size of a directory
du -hs .
or
du -sb
Copy directory with permission setting
cp -rp /path/to/directory
Store current directory
pushd . $popd ;dirs -l
Show disk usage
df -h
or
du -h
or
du -sk /var/log/* |sort -rn |head -10
Show current runlevel
runlevel
Switch runlevel
init 3
or
telinit 3
Permanently modify runlevel
1. edit /etc/init/rc-sysinit.conf
2. env DEFAULT_RUNLEVEL=2
Become root
su
Become somebody
su somebody
Report user quotes on device
requota -auvs
Get entries in a number of important databases
getent database_name
(e.g. the 'passwd' database)
getent passwd
//list all user account (all local and LDAP)
(e.g. fetch list of grop accounts)
getent group
//store in database 'group'
Change owner of file
chown user_name filename
chown -R user_name /path/to/directory/
//chown user:group filename
List current mount detail
df
List current usernames and user-numbers
cat /etc/passwd
Get all username
getent passwd| awk '{FS="[:]"; print $1}'
Show all users
compgen -u
Show all groups
compgen -g
Show group of user
group username
Show uid, gid, group of user
id username
Check if it's root
if [$(id -u) -ne 0];then
echo "You are not root!"
exit;
fi
//'id -u' output 0 if it's not root
Find out CPU information
more /proc/cpuinfo
or
lscpu
Set quota for user (e.g. disk soft limit: 120586240; hard limit: 125829120)
setquota username 120586240 125829120 0 0 /home
Show quota for user
quota -v username
Fork bomb
:(){:|:&};:
//dont try this at home
Check user login
lastlog
Edit path for all users
joe /etc/environment
//edit this file
Show running processes
ps aux
Find maximum number of processes
cat /proc/sys/kernal/pid_max
Show and set user limit
ulimit -u
Which ports are listening for TCP connections from the network
nmap -sT -O localhost
Print out number of cores/ processors
nproc --all
Check status of each core
- top
- press '1'
Show jobs and PID
jobs -l
List all running services
service --status-all
Schedule shutdown server
shutdown -r +5 "Server will restart in 5 minutes. Please save your work."
Cancel scheduled shutdown
shutdown -c
Boardcast to all users
wall -n hihi
Kill all process of a user
pkill -U user_name
Set gedit preference on server
-->you might have to install the following:
apt-get install libglib2.0-bin;
yum install dconf dconf-editor;
yum install dbus dbus-x11;
-->Check list
gsettings list-recursively
-->Change setting
e.g.
gsettings set org.gnome.gedit.preferences.editor highlight-current-line true
gsettings set org.gnome.gedit.preferences.editor scheme 'cobalt'
gsettings set org.gnome.gedit.preferences.editor use-default-font false
gsettings set org.gnome.gedit.preferences.editor editor-font 'Cantarell Regular 12'
Find out who has logged in on your system
--> [Quick] Printing out only the names:
users
--> [Detail] Printing out login time, load average, etc
w
Add user to a group (e.g add user 'nice' to the group 'docker', so that he can run docker without sudo)
sudo gpasswd -a nice docker
pip install python package without root
1. pip install --user package_name
2. You might need to export ~/.local/bin/ to PATH: export PATH=$PATH:~/.local/bin/
Removing old linux kernels (when /boot almost full...)
1. uname -a #check current kernel, which should NOT be removed
2. sudo apt-get purge linux-image-X.X.X-X-generic #replace old version
Change hostname
sudo hostname your-new-name
if not working, do also:
hostnamectl set-hostname your-new-hostname
then run:
hostnamectl
check /etc/hostname
if still not working..., edit:
/etc/sysconfig/network
/etc/sysconfig/network-scripts/ifcfg-ensxxx
add HOSTNAME="your-new-hostname"
List installed packages
apt list --installed
or Red Hat:
yum list installed
Tutorial for setting up your own DNS server
http://onceuponmine.blogspot.tw/2017/08/set-up-your-own-dns-server.html
Tutorial for creating a simple daemon
http://onceuponmine.blogspot.tw/2017/07/create-your-first-simple-daemon.html
=-=-=-=-=-A lot more coming!! =-=-=-=-=-=-=-=-=-=waitwait-=-=-=-=-=-=-=-=-=-