Create CODE_OF_CONDUCT.md

Repeat printing string n times

CODE_OF_CONDUCT.md

@@ -0,0 +1,76 @@
+# Contributor Covenant Code of Conduct
+
+## Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as
+contributors and maintainers pledge to making participation in our project and
+our community a harassment-free experience for everyone, regardless of age, body
+size, disability, ethnicity, sex characteristics, gender identity and expression,
+level of experience, education, socio-economic status, nationality, personal
+appearance, race, religion, or sexual identity and orientation.
+
+## Our Standards
+
+Examples of behavior that contributes to creating a positive environment
+include:
+
+* Using welcoming and inclusive language
+* Being respectful of differing viewpoints and experiences
+* Gracefully accepting constructive criticism
+* Focusing on what is best for the community
+* Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+* The use of sexualized language or imagery and unwelcome sexual attention or
+ advances
+* Trolling, insulting/derogatory comments, and personal or political attacks
+* Public or private harassment
+* Publishing others' private information, such as a physical or electronic
+ address, without explicit permission
+* Other conduct which could reasonably be considered inappropriate in a
+ professional setting
+
+## Our Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable
+behavior and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behavior.
+
+Project maintainers have the right and responsibility to remove, edit, or
+reject comments, commits, code, wiki edits, issues, and other contributions
+that are not aligned to this Code of Conduct, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+## Scope
+
+This Code of Conduct applies both within project spaces and in public spaces
+when an individual is representing the project or its community. Examples of
+representing a project or community include using an official project e-mail
+address, posting via an official social media account, or acting as an appointed
+representative at an online or offline event. Representation of a project may be
+further defined and clarified by project maintainers.
+
+## Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting the project team at nim.1111.ou@gmail.com. All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. The project team is
+obligated to maintain confidentiality with regard to the reporter of an incident.
+Further details of specific enforcement policies may be posted separately.
+
+Project maintainers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
+
+## Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
+available at https://www.contributor-covenant.org/version/1/4/code-of-conduct.html
+
+[homepage]: https://www.contributor-covenant.org
+
+For answers to common questions about this code of conduct, see
+https://www.contributor-covenant.org/faq

README.md

@@ -1,5 +1,5 @@
 # Bash-Oneliner
-I am glad that you are here! I started working on bioinformatics a few years ago (recently switched to cloud computing), and was amazed by those single-word bash commands which are much faster than my dull scripts, time saved through learning command-line shortcuts and scripting. Not all the code here is oneliner, but i put effort on making them brief and swift. I am mainly using Ubuntu, RedHat and Linux Mint and CentOS, sorry if the commands don't work on your system. 
+I am glad that you are here! I was working on bioinformatics a few years ago and was amazed by those single-word bash commands which are much faster than my dull scripts, time saved through learning command-line shortcuts and scripting. Recent years I am working on cloud computing and I keep recording those useful commands here. Not all of them is oneliner, but i put effort on making them brief and swift. I am mainly using Ubuntu, RedHat and Linux Mint and CentOS, sorry if the commands don't work on your system. 
 
 This blog will focus on simple bash commands for parsing data and Linux system maintenance that i acquired from work and LPIC exam. I apologize that there are no detailed citation for all the commands, but they are probably from dear Google and Stackoverflow.
 
@@ -8,7 +8,7 @@ If you know other cool commands, please teach me!
 
 Here's a more stylish version of [Bash-Oneliner](http://onceupon.github.io/Bash-Oneliner/)~
 
-## Handy Bash oneliner commands
+## Handy Bash one-liners
 
 - [Terminal Tricks](#terminal-tricks)
 - [Variable](#variable)
@@ -47,6 +47,7 @@ Ctrl + w : cut the word before the cursor; then Ctrl + y paste it
 Ctrl + u : cut the line before the cursor; then Ctrl + y paste it
 Ctrl + x + Ctrl + e : launch editor define by $EDITOR
 Ctrl + _ : undo typing.
+Ctrl + l : equivalent to clear.
 ```
 ##### Change case
 ```bash
@@ -90,6 +91,21 @@ Esc + c
 # run cat filename again
 ```
 
+##### Bash globbing
+```bash
+# '*' serves as a "wild card" for filename expansion.
+/b?n/?at      #/bin/cat
+
+# '?' serves as a single-character "wild card" for filename expansion.
+/etc/pa*wd    #/etc/passwd 
+
+# ‘[]’ serves to match the character from a range.
+ls -l [a-z]*   #list all files with alphabet in its filename.
+
+# ‘{}’ can be used to match filenames with more than one patterns
+ls {*.sh,*.py}   #list all .sh and .py files
+```
+
 ##### Some handy environment variables
 ```
 $0   :name of shell or shell script.  
@@ -99,10 +115,19 @@ $?   :most recent foreground pipeline exit status.
 $-   :current options set for the shell.  
 $$   :pid of the current shell (not subshell).  
 $!   :is the PID of the most recent background command.  
+
+$DESKTOP_SESSION     current display manager
+$EDITOR   preferred text editor.
+$LANG   current language.
+$PATH   list of directories to search for executable files (i.e. ready-to-run programs)
+$PWD    current directory
+$SHELL  current shell   
+$USER   current username
+$HOSTNAME   current hostname
 ```
 
 ## Grep
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 #####  Type of grep
 ```bash
@@ -284,7 +309,7 @@ grep -d skip 'bbo' /path/to/files/*
 
 
 ## Sed
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 ##### Remove the 1st line
 ```bash
 sed 1d filename
@@ -491,7 +516,7 @@ sed -r -e 's/^.{3}/&#/' file
 
 
 ## Awk
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### Set tab as field separator  
 ```bash
@@ -648,7 +673,7 @@ awk '{$6 = $4 - prev5; prev5 = $5; print;}'
 
 
 ## Xargs
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### Set tab as delimiter (default:space)
 ```bash
@@ -748,11 +773,6 @@ 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)
-```bash
-cat requirements.txt| xargs -n1 sudo pip install
-```
-
 ##### Count lines in all file, also count total lines
 ```bash
 ls|xargs wc -l
@@ -769,7 +789,7 @@ grep -rl '192.168.1.111' /etc | xargs sed -i 's/192.168.1.111/192.168.2.111/g'
 
 
 ## Find 
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 ##### List all sub directory/file in the current directory 
 ```bash
 find .
@@ -807,7 +827,7 @@ find . -name "*.mso" -size -74c -delete
 
 
 ## Condition and loop
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### If statement
 ```bash
@@ -906,7 +926,7 @@ esac
 ```
 
 ## Variable
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 ##### Variable substitution within quotes
 ```bash
 # foo=bar
@@ -967,8 +987,16 @@ echo ${var,,}
 helloworld
 ```
 
+
+##### Expand and then execute variable/argument
+```bash
+cmd="bar=foo"
+eval "$cmd"
+echo "$bar" # foo
+```
+
 ## Math
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 ##### Arithmetic Expansion in Bash (Operators: +, -, *, /, %, etc)
 ```bash
 echo $(( 10 + 5 ))  #15
@@ -1026,7 +1054,7 @@ echo "var=5;--var"| bc
 ```
 
 ## Time
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### Find out the time require for executing a command
 ```bash
@@ -1061,7 +1089,7 @@ job 1 at Wed Apr 18 11:16:00 2018
 
 
 ## Download
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### Download the content of this README.md (the one your are viewing now)
 ```bash
@@ -1122,9 +1150,20 @@ wget -O filename "http://example.com"
 wget -P /path/to/directory "http://example.com"
 ```
 
+##### Instruct curl to follow any redirect until it reaches the final destination:
+```bash
+curl -L google.com
+```
 
 ## Random
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
+##### Random generate password (e.g. generate 5 password each of length 13) 
+```bash
+sudo apt install pwgen
+pwgen 13 5
+#sahcahS9dah4a xieXaiJaey7xa UuMeo0ma7eic9 Ahpah9see3zai acerae7Huigh7
+```
+
 ##### Random pick 100 lines from a file 
 ```bash
 shuf -n 100 filename
@@ -1156,7 +1195,7 @@ echo $(((RANDOM %10)+1))
 ```
 
 ## Xwindow
-[[back to top](#handy-bash-oneliner-commands)]  
+[[back to top](#handy-bash-one-liners)]
 
 X11 GUI applications! Here are some GUI tools for you if you get bored by the text-only environment.  
 
@@ -1218,19 +1257,83 @@ xcowsay
 
 
 ## System
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
-# Check if it's root running
+##### Eliminate the zombie
+```bash
+# A zombie is already dead, so you cannot kill it. You can eliminate the zombie by killing its parent.
+# First, find PID of the zombie
+ps aux| grep 'Z'
+# Next find the PID of zombie's parent
+pstree -p -s <zombie_PID>
+# Then you can kill its parent and you will notice the zombie is gone.
+sudo kill 9 <parent_PID>
+```
+###### Show memory usage
+```bash
+free -c 10 -mhs 1
+# print 10 times, at 1 second interval
+```
+
+##### Display CPU and IO statistics for devices and partitions.
+```bash
+# refresh every second
+iostat -x -t 1
+```
+
+##### Display bandwidth usage on an network interface (e.g. enp175s0f0)
+```bash
+iftop -i enp175s0f0
+```
+
+##### Tell how long the system has been running and number of users
+```bash
+uptime
+```
+
+##### Check if it's root running
 ```bash
 if [ "$EUID" -ne 0 ]; then
         echo "Please run this as root"
         exit 1
 fi
 ```
+##### Change shell of a user (e.g. bonnie)
+```bash
+chsh -s /bin/sh bonnie 
+# /etc/shells: valid login shells
+```
+
+##### Change root / fake root / jail (e.g. change root to newroot)
+```bash
+chroot /home/newroot /bin/bash
+
+# To exit chroot
+exit
+```
+##### Display file status (size; access, modify and change time, etc) of a file (e.g. filename.txt)
+```bash
+stat filename.txt
+```
 
 ##### Snapshot of the current processes
 ```bash
-ps 
+ps aux
+```
+
+##### Display a tree of processes
+```bash
+pstree
+```
+
+##### Find maximum number of processes
+```bash
+cat /proc/sys/kernel/pid_max
+```
+
+##### Print or control the kernel ring buffer
+```bash
+dmesg
 ```
 
 ##### Show IP address
@@ -1241,6 +1344,27 @@ $ip add show
 ifconfig
 ```
 
+##### Print previous and current SysV runlevel
+```bash
+runlevel
+
+# or
+who -r
+```
+
+##### Change SysV runlevel (e.g. 5)
+```bash
+init 5
+#or
+telinit 5
+```
+
+##### Display all available services in all runlevels,
+```bash
+chkconfig --list
+# update-rc.d equivalent to chkconfig in ubuntu
+```
+
 ##### Check system version
 ```bash
 cat /etc/*-release
@@ -1251,11 +1375,29 @@ cat /etc/*-release
 man hier
 ```
 
+##### Control the systemd system and service manager
+```bash
+# e.g. check the status of cron service
+systemctl status cron.service
+
+# e.g. stop cron service
+systemctl stop cron.service
+```
+
 ##### List job
 ```bash
 jobs -l
 ```
 
+##### Run a program with modified priority (e.g. ./test.sh)
+```bash
+# nice value is adjustable from -20 (most favorable) to +19
+# the nicer the application, the lower the priority 
+# Default niceness: 10; default priority: 80
+
+nice -10 ./test.sh
+```
+
 ##### Export PATH
 ```bash
 export PATH=$PATH:~/path/you/want
@@ -1267,8 +1409,11 @@ chmod +x filename
 # you can now ./filename to execute it
 ```
 
-##### Check system (x86-64)
+##### Print system information
 ```bash
+uname -a
+
+# Check system hardware-platform (x86-64)
 uname -i
 ```
 
@@ -1297,15 +1442,36 @@ passwd username
 2. alias pd="pwd" //no more need to type that 'w'!
 3. source ~/.bash_profile
 ```
+##### Print all alias
+```bash
+alias -p
+```
+
+##### Unalias (e.g. after alias ls='ls --color=auto')
+```bash
+unalias ls
+```
+
+##### Set and unset shell options
+```bash
+# print all shell options
+shopt
+
+# to unset (or stop) alias
+shopt -u expand_aliases
+
+# to set (or start) alias
+shopt -s expand_aliases
+```
 
 ##### List environment variables (e.g. PATH) 
 ```bash
-$echo $PATH
+echo $PATH
 # list of directories separated by a colon
 ```
 ##### List all environment variables for current user
 ```bash
-$env
+env
 ```
 ##### Unset environment variable (e.g. unset variable 'MYVAR')
 ```bash
@@ -1317,6 +1483,11 @@ unset MYVAR
 lsblk
 ```
 
+##### Inform the OS of partition table changes
+```bash
+partprobe
+```
+
 ##### Soft link program to bin
 ```bash
 ln -s /path/to/program /home/usr/bin
@@ -1338,7 +1509,7 @@ rsh node_name
 netstat -tulpn
 ```
 
-##### Find which link to a file
+##### Print resolved symbolic links or canonical file names
 ```bash
 readlink filename
 ```
@@ -1411,6 +1582,7 @@ init 3
 #or
 telinit 3 
 ```
+
 ##### Permanently modify runlevel  
 ```bash
 1. edit /etc/init/rc-sysinit.conf 
@@ -1452,8 +1624,19 @@ chown -R user_name /path/to/directory/
 # chown user:group filename
 ```
 
+##### Mount and unmount 
+```bash
+# e.g. Mount /dev/sdb to /home/test
+mount /dev/sdb /home/test
+
+# e.g. Unmount /home/test
+umount /home/test
+```
+
 ##### List current mount detail
 ```bash
+mount
+# or
 df
 ```
 
@@ -1514,12 +1697,14 @@ setquota username 120586240 125829120 0 0 /home
 quota -v username
 ```
 
-##### Fork bomb
-# Don't try this at home!
-# It is a function that calls itself twice every call until you run out of system resources.
-# A '# ' is added in front for safety reason, remove it when seriously you are testing it. 
+##### Display current libraries from the cache
 ```bash
-# :(){:|:&};:
+ldconfig -p
+```
+
+##### Print shared library dependencies (e.g. for 'ls')
+```bash
+ldd /bin/ls
 ```
 
 ##### Check user login
@@ -1533,20 +1718,11 @@ joe /etc/environment
 # edit this file
 ```
 
-##### Show running processes
-```bash
-ps aux
-```
-
-##### Find maximum number of processes
-```bash
-cat /proc/sys/kernal/pid_max
-```
-
 ##### Show and set user limit
 ```bash
 ulimit -u
 ```
+
 ##### Which ports are listening for TCP connections from the network
 ```bash
 nmap -sT -O localhost
@@ -1827,7 +2003,7 @@ systemctl list-unit-files|grep enabled
 
 
 ## Hardware
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### Collect and summarize all hardware info of your machine
 ```bash
@@ -1899,11 +2075,34 @@ lsblk -io KNAME,TYPE,MODEL,VENDOR,SIZE,ROTA
 #where ROTA means rotational device / spinning hard disks (1 if true, 0 if false)
 ```
 
-##### List information about NIC
+##### List all PCI (Peripheral Component Interconnect) devices
 ```bash
+lspci
+# List information about NIC
 lspci | egrep -i --color 'network|ethernet'
 ```
 
+##### List all USB devices
+```bash
+lsusb
+```
+
+##### Linux modules
+```bash
+# Show the status of modules in the Linux Kernel
+lsmod
+
+# Add and remove modules from the Linux Kernel
+modprobe
+
+# or
+# Remove a module 
+rmmod
+
+# Insert a module
+insmod
+```
+
 ##### Controlling IPMI-enabled devices (e.g. BMC)
 ```bash
 # Remotely finding out power status of the server
@@ -1932,7 +2131,7 @@ ipmitool -I bmc lan set 1 defgw ipaddr 192.168.0.1
 
 
 ## Networking
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
 
 ##### Display IP address
 ```bash
@@ -1981,7 +2180,24 @@ hostnamectl set-hostname "mynode"
 
 
 ## Others
-[[back to top](#handy-bash-oneliner-commands)]
+[[back to top](#handy-bash-one-liners)]
+
+##### Repeat printing string n times (e.g. print 'hello world' five times)
+```bash
+printf 'hello world\n%.0s' {1..5}
+```
+
+##### Encode strings as Base64 strings
+```bash
+echo test|base64
+#dGVzdAo=
+```
+
+##### Do not echo the trailing newline
+```bash
+username=`echo -n "bashoneliner"`
+```
+
 ##### Get parent directory of current directory
 ```bash
 dirname `pwd`
@@ -2071,8 +2287,7 @@ zmore filename
 zless filename
 ```
 
-##### Run in background, output error file
-    
+##### Run command in background, output error file
 ```bash
 some_commands  &>log &
 
@@ -2090,6 +2305,21 @@ some_commands 2>&1 >>outfile
 #0: standard input; 1: standard output; 2: standard error
 ```
 
+##### Run multiple commands in background
+```bash
+# run sequentially
+(sleep 2; sleep 3) &
+
+# run parallelly 
+sleep 2 & sleep 3 &
+```
+
+##### Run process even when logout (immune to hangups, with output to a non-tty)
+```bash
+# e.g. Run myscript.sh even when log out.
+nohup bash myscript.sh
+```
+
 ##### Send mail 
 ```bash
 echo 'heres the content'| mail -a /path/to/attach_file.txt -s 'mail.subject' me@gmail.com
@@ -2239,6 +2469,8 @@ file=${1#*.}
 ##### Python simple HTTP Server
 ```bash
 python -m SimpleHTTPServer
+# or when using python3:
+python3 -m http.server
 ```
 
 ##### Read user input
@@ -2332,6 +2564,15 @@ basename filename.gz .gz
 
 zcat filename.gz> $(basename filename.gz .gz).unpacked
 ```
+
+##### Fork bomb
+```bash
+# Don't try this at home!
+# It is a function that calls itself twice every call until you run out of system resources.
+# A '# ' is added in front for safety reason, remove it when seriously you are testing it. 
+# :(){:|:&};:
+```
+
 ##### Add file extension to all file(e.g add .txt)
 ```bash
 rename s/$/.txt/ *
@@ -2605,19 +2846,24 @@ script output.txt
 # to logout the screen session (stop saving the contents), type exit.
 ```
 
-##### list contents of directories in a tree-like format.
+##### List contents of directories in a tree-like format.
 ```bash
 tree
 # go to the directory you want to list, and type tree (sudo apt-get install tree)
 # output:
-# one/
-# └── two
+# home/
+# └── project
 #     ├── 1
 #     ├── 2
 #     ├── 3
 #     ├── 4
 #     └── 5
 #
+
+# set level directories deep (e.g. level 1)
+tree -L 1
+# home/
+# └── project
 ```
 
 ##### Set up virtualenv(sandbox) for python