Bash-Oneliner

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.

English and bash are not my first language, please correct me anytime, thank you. If you know other cool commands, please teach me!

Here's a more stylish version of Bash-Oneliner~

Handy Bash one-liners

Terminal Tricks

Using Ctrl keys

Ctrl + n : same as Down arrow. Ctrl + p : same as Up arrow. Ctrl + r : begins a backward search through command history.(keep pressing Ctrl + r to move backward) Ctrl + s : to stop output to terminal. Ctrl + q : to resume output to terminal after Ctrl + s. Ctrl + a : move to the beginning of line. Ctrl + e : move to the end of line. Ctrl + d : if you've type something, Ctrl + d deletes the character under the cursor, else, it escapes the current shell. Ctrl + k : delete all text from the cursor to the end of line. Ctrl + x + backspace : delete all text from the beginning of line to the cursor. Ctrl + t : transpose the character before the cursor with the one under the cursor, press Esc + t to transposes the two words before the cursor. 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 + _ : undo typing. Ctrl + l : equivalent to clear. Ctrl + x + Ctrl + e : launch editor defined by $EDITOR to input your command. Useful for multi-line commands.

Change case

Esc + u # converts text from cursor to the end of the word to uppercase. Esc + l # converts text from cursor to the end of the word to lowercase. Esc + c # converts letter under the cursor to uppercase.

Run history number (e.g. 53)

!53

Run last command

!!

Run last command and change some parameter using caret substitution (e.g. last command: echo 'aaa' -> rerun as: echo 'bbb')

#last command: echo 'aaa' ^aaa^bbb #echo 'bbb' #bbb #Notice that only the first aaa will be replaced, if you want to replace all 'aaa', use ':&' to repeat it: ^aaa^bbb^:& #or !!:gs/aaa/bbb/

Run past command that began with (e.g. cat filename)

!cat # or !c # run cat filename again

Bash globbing

# '*' 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. $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. $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

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Type of grep

grep = grep -G # Basic Regular Expression (BRE) fgrep = grep -F # fixed text, ignoring meta-charachetrs egrep = grep -E # Extended Regular Expression (ERE) pgrep = grep -P # Perl Compatible Regular Expressions (PCRE) rgrep = grep -r # recursive

Grep and count number of empty lines

grep -c "^$"

Grep and return only integer

grep -o '[0-9]*' #or grep -oP '\d'

Grep integer with certain number of digits (e.g. 3)

grep ‘[0-9]\{3\}’ # or grep -E ‘[0-9]{3}’ # or grep -P ‘\d{3}’

Grep only IP address

grep -Eo '[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}' # or grep -Po '\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}'

Grep whole word (e.g. 'target')

grep -w 'target' #or using RE grep '\btarget\b'

Grep returning lines before and after match (e.g. 'bbo')

# return also 3 lines after match grep -A 3 'bbo' # return also 3 lines before match grep -B 3 'bbo' # return also 3 lines before and after match grep -C 3 'bbo'

Grep string starting with (e.g. 'S')

grep -o 'S.*'

Extract text between words (e.g. w1,w2)

grep -o -P '(?<=w1).*(?=w2)'

Grep lines without word (e.g. bbo)

grep -v bbo filename

Grep lines not begin with string (e.g. #)

grep -v '^#' file.txt

Grep variables with space within it (e.g. bbo="some strings")

grep "$boo" filename #remember to quote the variable!

Grep only one/first match (e.g. bbo)

grep -m 1 bbo filename

Grep and return number of matching line(e.g. bbo)

grep -c bbo filename

Count occurrence (e.g. three times a line count three times)

grep -o bbo filename |wc -l

Case insensitive grep (e.g. bbo/BBO/Bbo)

grep -i "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, do not ouput the filenames (e.g. bbo)

grep -rh bbo /path/to/directory

Search all files in directory, output ONLY the filenames with matches(e.g. bbo)

grep -rl 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'

Regex any singer character (e.g. ACB or AEB)

grep 'A.B'

Regex with or without a certain character (e.g. color or colour)

grep ‘colou?r’

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

Skip directory (e.g. bbo)

grep -d skip 'bbo' /path/to/files/*

Sed

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Remove the 1st line

sed 1d filename

Remove the first 100 lines (remove line 1-100)

sed 1,100d filename

Remove lines with string (e.g. bbo)

sed "/bbo/d" filename - case insensitive: sed "/bbo/Id" filename

Remove lines whose nth character not equal to a value (e.g. 5th character not equal to 2)

sed -E '/^.{5}[^2]/d' #aaaa2aaa (you can stay) #aaaa1aaa (delete!)

Edit infile (edit and save)

sed -i "/bbo/d" filename

When using variable (e.g. $i), use double quotes " "

# e.g. add >$i to the first line (to make a bioinformatics FASTA file) sed "1i >$i" # notice the double quotes! in other examples, you can use a single quote, but here, no way! # '1i' means insert to first line

Using environment variable and end-of-line pattern at the same time.

# Use backslash for end-of-line $ pattern, and double quotes for expressing the variable sed -e "\$s/\$/\n+--$3-----+/"

Delete/remove empty lines

sed '/^\s*$/d' # or sed '/^$/d'

Delete/remove last line

sed '$d'

Delete/remove last character from end of file

sed -i '$ s/.$//' filename

Add string to beginning of file (e.g. "[")

sed -i '1s/^/[/' file

Add string at certain line number (e.g. add 'something' to line 1 and line 3)

sed -e '1isomething -e '3isomething'

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 separate by ",")

sed -s '$a,' *.json > all.json

Substitution (e.g. replace A by B)

sed 's/A/B/g' filename

Substitution with wildcard (e.g. replace a line start with aaa= by aaa=/my/new/path)

sed "s/aaa=.*/aaa=\/my\/new\/path/g"

Select lines start with string (e.g. bbo)

sed -n '/^@S/p'

Delete lines with string (e.g. bbo)

sed '/bbo/d' filename

Print/get/trim a range of line (e.g. line 500-5000)

sed -n 500,5000p 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 # To 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 particular line (e.g. 123th line)

sed -n -e '123p'

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

sed '$ s/.$//'

Insert character at specified position of file (e.g. AAAAAA --> AAA#AAA)

sed -r -e 's/^.{3}/&#/' file

Awk

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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 occurrence 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

Remove last column

awk 'NF{NF-=1};1' file

Usage and meaning of NR and FNR

# For example there are two files: # 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

# For example there are two files: # 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

# For example, seperate the following content: # David cat,dog # into # David cat # David dog awk '{split($2,a,",");for(i in a)print $1"\t"a[i]}' file # Detail here:　http://stackoverflow.com/questions/33408762/bash-turning-single-comma-separated-column-into-multi-line-string

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

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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 # when using a backtick rm `find . -name "*.html"`

Delete files 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

Count lines in all file, also count total lines

ls|xargs wc -l

Xargs and grep

cat grep_list |xargs -I{} grep {} filename

Xargs and sed (replace all old ip address with new ip address under /etc directory)

grep -rl '192.168.1.111' /etc | xargs sed -i 's/192.168.1.111/192.168.2.111/g'

Find

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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 there are 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

Condition and loop

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If statement

# if and else loop for string matching if [[ "$c" == "read" ]]; then outputdir="seq"; else outputdir="write" ; fi # Test if myfile contains the string 'test': if grep -q hello myfile; then … # Test if mydir is a directory, change to it and do other stuff: if cd mydir; then echo 'some content' >myfile else echo >&2 "Fatal error. This script requires mydir." fi # if variable is null if [ ! -s "myvariable" ] #True of the length if "STRING" is zero. # Test if file exist if [ -e 'filename' ] then echo -e "file exists!" fi # Test if file exist but also including symbolic links: if [ -e myfile ] || [ -L myfile ] then echo -e "file exists!" fi # Test if the value of x is greater or equal than 5 if [ "$x" -ge 5 ]; then … # Test if the value of x is greater or equal than 5, in bash/ksh/zsh: if ((x >= 5)); then … # Use (( )) for arithmetic operation if ((j==u+2)) # Use [[ ]] for comparison if [[ $age -gt 21 ]]

More if commands

For loop

for i in $(ls); do echo file $i;done #or for i in *; do echo file $i; done # Press any key to continue each loop for i in $(cat tpc_stats_0925.log |grep failed|grep -o '\query\w\{1,2\}');do cat ${i}.log; read -rsp $'Press any key to continue...\n' -n1 key;done # Print a file line by line when a key is pressed, oifs="$IFS"; IFS=$'\n'; for line in $(cat myfile); do ...; done while read -r line; do ...; done <myfile #If only one word a line, simply for line in $(cat myfile); do echo $line; read -n1; done #Loop through an array for i in "${arrayName[@]}"; do echo $i;done

While loop,

# Column subtraction of a file (e.g. a 3 columns file) while read a b c; do echo $(($c-$b));done < <(head filename) #there is a space between the two '<'s # Sum up column subtraction i=0; while read a b c; do ((i+=$c-$b)); echo $i; done < <(head filename) # Keep checking a running process (e.g. perl) and start another new process (e.g. python) immediately after it. (BETTER use the wait command! Ctrl+F 'wait') while [[ $(pidof perl) ]];do echo f;sleep 10;done && python timetorunpython.py

switch (case in bash)

read type; case $type in '0') echo 'how' ;; '1') echo 'are' ;; '2') echo 'you' ;; esac

Variable

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Variable substitution within quotes

# foo=bar echo "'$foo'" #'bar' # double/single quotes around single quotes make the inner single quotes expand variables

Get the length of variable

var="some string" echo ${#var} # 11

Get the first character of the variable

var=string echo "${var:0:1}" #s # or echo ${var%%"${var#?}"}

Remove the first or last string from variable

var="some string" echo ${var:2} #me string

Replacement (e.g. remove the first leading 0 )

var="0050" echo ${var[@]#0} #050

Replacement (e.g. replace 'a' with ',')

{var/a/,}

Replace all (e.g. replace all 'a' with ',')

{var//a/,}

#with grep test="god the father" grep ${test// /\\\|} file.txt # turning the space into 'or' (\|) in grep

To change the case of the string stored in the variable to lowercase (Parameter Expansion)

var=HelloWorld echo ${var,,} helloworld

Expand and then execute variable/argument

cmd="bar=foo" eval "$cmd" echo "$bar" # foo

Math

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Arithmetic Expansion in Bash (Operators: +, -, *, /, %, etc)

echo $(( 10 + 5 )) #15 x=1 echo $(( x++ )) #1 , notice that it is still 1, since it's post-incremen echo $(( x++ )) #2 echo $(( ++x )) #4 , notice that it is not 3 since it's pre-incremen echo $(( x-- )) #4 echo $(( x-- )) #3 echo $(( --x )) #1 x=2 y=3 echo $(( x ** y )) #8

Print out the prime factors of a number (e.g. 50)

factor 50

Sum up input list (e.g. seq 10)

seq 10|paste -sd+|bc

Sum up a file (each line in file contains only one number)

awk '{s+=$1} END {print s}' filename

Column subtraction

cat file| awk -F '\t' 'BEGIN {SUM=0}{SUM+=$3-$2}END{print SUM}'

Simple math with expr

expr 10+20 #30 expr 10\*20 #600 expr 30 \> 20 #1 (true)

More math with bc

# Number of decimal digit/ significant figure echo "scale=2;2/3" | bc #.66 # Exponent operator echo "10^2" | bc #100 # Using variables echo "var=5;--var"| bc #4

Time

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Find out the time require for executing a command

time echo hi

Wait for some time (e.g 10s)

sleep 10

Log out your account after a certain period of time (e.g 10 seconds)

TMOUT=10 #once you set this variable, logout timer start running!

Set how long you want to run a command

#This will run the command 'sleep 10' for only 1 second. timeout 1 sleep 10

Set when you want to run a command (e.g 1 min from now)

at now + 1min #time-units can be minutes, hours, days, or weeks warning: commands will be executed using /bin/sh at> echo hihigithub >~/itworks at> <EOT> # press Ctrl + D to exit job 1 at Wed Apr 18 11:16:00 2018

Download

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Download the content of this README.md (the one your are viewing now)

curl https://raw.githubusercontent.com/onceupon/Bash-Oneliner/master/README.md | pandoc -f markdown -t man | man -l - # or w3m (a text based web browser and pager) curl https://raw.githubusercontent.com/onceupon/Bash-Oneliner/master/README.md | pandoc | w3m -T text/html # or using emacs (in emac text editor) emacs --eval '(org-mode)' --insert <(curl https://raw.githubusercontent.com/onceupon/Bash-Oneliner/master/README.md | pandoc -t org) # or using emacs (on terminal, exit using Ctrl + x then Ctrl + c) emacs -nw --eval '(org-mode)' --insert <(curl https://raw.githubusercontent.com/onceupon/Bash-Oneliner/master/README.md | pandoc -t org)

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 (separate 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 a file (e.g. filename.txt): 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 # Next you can download it by: 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"

Instruct curl to follow any redirect until it reaches the final destination:

curl -L google.com

Random

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Random generate password (e.g. generate 5 password each of length 13)

sudo apt install pwgen pwgen 13 5 #sahcahS9dah4a xieXaiJaey7xa UuMeo0ma7eic9 Ahpah9see3zai acerae7Huigh7

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

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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 xcowsay

Open pictures/images from ssh server

1. ssh -X user_name@ip_address 2. apt-get install eog 3. eog picture.png

Watch videos on server

1. ssh -X user_name@ip_address 2. sudo apt install mpv 3. mpv myvideo.mp4

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

System

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Follow the most recent logs from service

journalctl -u <service_name> -f

Eliminate the zombie

# 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

free -c 10 -mhs 1 # print 10 times, at 1 second interval

Display CPU and IO statistics for devices and partitions.

# refresh every second iostat -x -t 1

Display bandwidth usage on an network interface (e.g. enp175s0f0)

iftop -i enp175s0f0

Tell how long the system has been running and number of users

uptime

Check if it's root running

if [ "$EUID" -ne 0 ]; then echo "Please run this as root" exit 1 fi

Change shell of a user (e.g. bonnie)

chsh -s /bin/sh bonnie # /etc/shells: valid login shells

Change root / fake root / jail (e.g. change root to newroot)

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)

stat filename.txt

Snapshot of the current processes

ps aux

Display a tree of processes

pstree

Find maximum number of processes

cat /proc/sys/kernel/pid_max

Print or control the kernel ring buffer

dmesg

Show IP address

$ip add show # or ifconfig

Print previous and current SysV runlevel

runlevel # or who -r

Change SysV runlevel (e.g. 5)

init 5 #or telinit 5

Display all available services in all runlevels,

chkconfig --list # update-rc.d equivalent to chkconfig in ubuntu

Check system version

cat /etc/*-release

Linux Programmer's Manuel: hier- description of the filesystem hierarchy

man hier

Control the systemd system and service manager

# e.g. check the status of cron service systemctl status cron.service # e.g. stop cron service systemctl stop cron.service

List job

jobs -l

Run a program with modified priority (e.g. ./test.sh)

# 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

export PATH=$PATH:~/path/you/want

Make file executable

chmod +x filename # you can now ./filename to execute it

Print system information

uname -a # Check system hardware-platform (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

Print all alias

alias -p

Unalias (e.g. after alias ls='ls --color=auto')

unalias ls

Set and unset shell options

# 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)

echo $PATH # list of directories separated by a colon

List all environment variables for current user

env

Unset environment variable (e.g. unset variable 'MYVAR')

unset MYVAR

Show partition format

lsblk

Inform the OS of partition table changes

partprobe

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

Print resolved symbolic links or canonical file names

readlink filename

Find out the type of command and where it link to (e.g. python)

type python # python is /usr/bin/python # There are 5 different types, check using the 'type -f' flag # 1. alias (shell alias) # 2. function (shell function, type will also print the function body) # 3. builtin (shell builtin) # 4. file (disk file) # 5. keyword (shell reserved word) # You can also use `which` which python # /usr/bin/python

List all functions names

declare -F

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 . # then pop popd #or use dirs to display the list of currently remembered directories. 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

repquota -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

Mount and unmount

# 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

mount # or 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

Display current libraries from the cache

ldconfig -p

Print shared library dependencies (e.g. for 'ls')

ldd /bin/ls

Check user login

lastlog

Edit path for all users

joe /etc/environment # edit this file

Show and set user limit

ulimit -u

Which ports are listening for TCP connections from the network

nmap -sT -O localhost #notice that some companies might not like you using nmap

Print out number of cores/ processors

nproc --all

Check status of each core

1. top 2. 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

Broadcast to all users

wall -n hihi

Kill all process of a user

pkill -U user_name

Kill all process of a program

kill -9 $(ps aux | grep 'program_name' | awk '{print $2}')

Set gedit preference on server

# You might have to install the following: apt-get install libglib2.0-bin; # or yum install dconf dconf-editor; yum install dbus dbus-x11; # Check list gsettings list-recursively # Change some settings 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'

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 check with: hostnamectl # Or 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 on Red Hat: yum list installed

Check which file make the device busy on umount

lsof /mnt/dir

When sound not working

killall pulseaudio # then press Alt-F2 and type in pulseaudio

When sound not working

killall pulseaudio

List information about SCSI devices

lsscsi

Using telnet to test open ports, test if you can connect to a port (e.g 53) of a server (e.g 192.168.2.106)

telnet 192.168.2.106 53

Change network maximum transmission unit (mtu) (e.g. change to 9000)

ifconfig eth0 mtu 9000

Get pid of a running process (e.g python)

pidof python # or ps aux|grep python

NTP

# Start ntp: ntpd # Check ntp: ntpq -p

Remove unnecessary files to clean your server

sudo apt-get autoremove sudo apt-get clean sudo rm -rf ~/.cache/thumbnails/* # Remove old kernal: sudo dpkg --list 'linux-image*' sudo apt-get remove linux-image-OLDER_VERSION

Increase/ resize root partition (root partition is an LVM logical volume)

pvscan lvextend -L +130G /dev/rhel/root -r # Adding -r will grow filesystem after resizing the volume.

Create a UEFI Bootable USB drive (e.g. /dev/sdc1)

sudo dd if=~/path/to/isofile.iso of=/dev/sdc1 oflag=direct bs=1048576

Locate and remove a package

sudo dpkg -l | grep <package_name> sudo dpkg --purge <package_name>

Create a ssh tunnel

ssh -f -L 9000:targetservername:8088 root@192.168.14.72 -N #-f: run in background; -L: Listen; -N: do nothing #the 9000 of your computer is now connected to the 8088 port of the targetservername through 192.168.14.72 #so that you can see the content of targetservername:8088 by entering localhost:9000 from your browser.

Get process ID of a process (e.g. sublime_text)

#pidof pidof sublime_text #pgrep, you don't have to type the whole program name pgrep sublim #pgrep, echo 1 if process found, echo 0 if no such process pgrep -q sublime_text && echo 1 || echo 0 #top, takes longer time top|grep sublime_text

Some benchmarking tools for your server

aio-stress - AIO benchmark. bandwidth - memory bandwidth benchmark. bonnie++ - hard drive and file system performance benchmark. dbench - generate I/O workloads to either a filesystem or to a networked CIFS or NFS server. dnsperf - authorative and recursing DNS servers. filebench - model based file system workload generator. fio - I/O benchmark. fs_mark - synchronous/async file creation benchmark. httperf - measure web server performance. interbench - linux interactivity benchmark. ioblazer - multi-platform storage stack micro-benchmark. iozone - filesystem benchmark. iperf3 - measure TCP/UDP/SCTP performance. kcbench - kernel compile benchmark, compiles a kernel and measures the time it takes. lmbench - Suite of simple, portable benchmarks. netperf - measure network performance, test unidirectional throughput, and end-to-end latency. netpipe - network protocol independent performance evaluator. nfsometer - NFS performance framework. nuttcp - measure network performance. phoronix-test-suite - comprehensive automated testing and benchmarking platform. seeker - portable disk seek benchmark. siege - http load tester and benchmark. sockperf - network benchmarking utility over socket API. spew - measures I/O performance and/or generates I/O load. stress - workload generator for POSIX systems. sysbench - scriptable database and system performance benchmark. tiobench - threaded IO benchmark. unixbench - the original BYTE UNIX benchmark suite, provide a basic indicator of the performance of a Unix-like system. wrk - HTTP benchmark.

Show a listing of last logged in users.

lastb

Show a listing of current logged in users, print information of them

who

Show who is logged on and what they are doing

Print the user names of users currently logged in to the current host.

users

Stop tailing a file on program terminate

tail -f --pid=<PID> filename.txt # replace <PID> with the process ID of the program.

List all enabled services

systemctl list-unit-files|grep enabled

Hardware

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Collect and summarize all hardware info of your machine

lshw -json >report.json # Other options are: [ -html ] [ -short ] [ -xml ] [ -json ] [ -businfo ] [ -sanitize ] ,etc

Finding Out memory device detail

sudo dmidecode -t memory

Print detail of CPU hardware

dmidecode -t 4 # Type Information # 0 BIOS # 1 System # 2 Base Board # 3 Chassis # 4 Processor # 5 Memory Controller # 6 Memory Module # 7 Cache # 8 Port Connector # 9 System Slots # 11 OEM Strings # 13 BIOS Language # 15 System Event Log # 16 Physical Memory Array # 17 Memory Device # 18 32-bit Memory Error # 19 Memory Array Mapped Address # 20 Memory Device Mapped Address # 21 Built-in Pointing Device # 22 Portable Battery # 23 System Reset # 24 Hardware Security # 25 System Power Controls # 26 Voltage Probe # 27 Cooling Device # 28 Temperature Probe # 29 Electrical Current Probe # 30 Out-of-band Remote Access # 31 Boot Integrity Services # 32 System Boot # 34 Management Device # 35 Management Device Component # 36 Management Device Threshold Data # 37 Memory Channel # 38 IPMI Device # 39 Power Supply

Count the number of Segate hard disks

lsscsi|grep SEAGATE|wc -l # or sg_map -i -x|grep SEAGATE|wc -l

Get UUID of a disk (e.g. sdb)

blkid /dev/sdb

Print detail of all hard disks

lsblk -io KNAME,TYPE,MODEL,VENDOR,SIZE,ROTA #where ROTA means rotational device / spinning hard disks (1 if true, 0 if false)

List all PCI (Peripheral Component Interconnect) devices

lspci # List information about NIC lspci | egrep -i --color 'network|ethernet'

List all USB devices

lsusb

Linux modules

# 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)

# Remotely finding out power status of the server ipmitool -U <bmc_username> -P <bmc_password> -I lanplus -H <bmc_ip_address> power status # Remotely switching on server ipmitool -U <bmc_username> -P <bmc_password> -I lanplus -H <bmc_ip_address> power on # Turn on panel identify light (default 15s) ipmitool chassis identify 255 # Found out server sensor temperature ipmitool sensors |grep -i Temp # Reset BMC ipmitool bmc reset cold # Prnt BMC network ipmitool lan print 1 # Setting BMC network ipmitool -I bmc lan set 1 ipaddr 192.168.0.55 ipmitool -I bmc lan set 1 netmask 255.255.255.0 ipmitool -I bmc lan set 1 defgw ipaddr 192.168.0.1

Networking

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Display IP address

ip a

Display route table

ip r

Display ARP cache (ARP cache displays the MAC addresses of device in the same network that you have connected to)

ip n

Add transient IP addres (reset after reboot) (e.g. add 192.168.140.3/24 to device eno16777736)

ip address add 192.168.140.3/24 dev eno16777736

Persisting network configuration changes

sudo vi /etc/sysconfig/network-scripts/ifcfg-enoxxx # then edit the fields: BOOTPROT, DEVICE, IPADDR, NETMASK, GATEWAY, DNS1 etc

Refresh NetworkManager

sudo nmcli c reload

Restart all interfaces

sudo systemctl restart network.service

To view hostname, OS, kernal, architecture at the same time!

hostnamectl

Set hostname (set all transient, static, pretty hostname at once)

hostnamectl set-hostname "mynode"

Others

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Repeat printing string n times (e.g. print 'hello world' five times)

printf 'hello world\n%.0s' {1..5}

Encode strings as Base64 strings

echo test|base64 #dGVzdAo=

Do not echo the trailing newline

username=`echo -n "bashoneliner"`

Get parent directory of current directory

dirname `pwd`

Copy a file to multiple files (e.g copy fileA to file(B-D))

tee <fileA fileB fileC fileD >/dev/null

Remove newline / nextline

tr --delete '\n' <input.txt >output.txt

Replace newline

tr '\n' ' ' <filename

To uppercase/lowercase

tr /a-z/ /A-Z/

Translate a range of characters (e.g. substitute a-z into a)

echo 'something' |tr a-z a # aaaaaaaaa

Compare two 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

Compare two files, strip trailing carriage return/ nextline (e.g. fileA, fileB)

 diff fileA fileB --strip-trailing-cr

Number a file (e.g. fileA)

nl fileA #or nl -nrz fileA # add leading zeros #or nl -w1 -s ' ' # making it simple, blank separate

Join two files field by field with tab (default join by the first column of both file, and default separator is space)

# fileA and fileB should have the same ordering of lines. join -t '\t' fileA fileB # Join using specified field (e.g. column 3 of fileA and column 5 of fileB) join -1 3 -2 5 fileA fileB

Combine/ paste two or more files into columns (e.g. fileA, fileB, fileC)

paste fileA fileB fileC # default tab separate

Reverse string

echo 12345| rev

Read .gz file without extracting

zmore filename # or zless filename

Run command in background, output error file

some_commands &>log & # or some_commands 2>log & # or some_commands 2>&1| tee logfile # or some_commands |& tee logfile # or some_commands 2>&1 >>outfile #0: standard input; 1: standard output; 2: standard error

Run multiple commands in background

# 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)

# e.g. Run myscript.sh even when log out. nohup bash myscript.sh

Send mail

echo 'heres the content'| mail -a /path/to/attach_file.txt -s 'mail.subject' me@gmail.com # use -a flag to set send from (-a "From: some@mail.tld")

Convert .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>!$

Extract .xf

unxz filename.tar.xz # then 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

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 "."

Python simple HTTP Server

python -m SimpleHTTPServer # or when using python3: python3 -m http.server

Read user input

read input echo $input

Generate sequence 1-10

seq 10

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=() # or declare array=() # or associative array declare -A array=()

Send a directory

scp -r directoryname user@ip:/path/to/send

Split file into smaller file

# Split by line (e.g. 1000 lines/smallfile) split -d -l 1000 largefile.txt # Split by byte without breaking lines across files split -C 10 largefile.txt

Create a large amount of dummy files (e.g 100000 files, 10 bytes each):

#1. Create a big file dd if=/dev/zero of=bigfile bs=1 count=1000000 #2. Split the big file to 100000 10-bytes files split -b 10 -a 10 bigfile

Rename all files (e.g. remove ABC from all .gz files)

rename 's/ABC//' *.gz

Remove file extension (e.g remove .gz from filename.gz)

basename filename.gz .gz zcat filename.gz> $(basename filename.gz .gz).unpacked

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. # :(){:|:&};:

Add file extension to all file(e.g add .txt)

rename s/$/.txt/ * # You can use rename -n s/$/.txt/ * to check the result first, it will only print sth like this: # rename(a, a.txt) # rename(b, b.txt) # rename(c, c.txt)

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/ i++ a numeric variable (e.g. $var)

((var++)) # or var=$((var+1))

Clear the contents of a file (e.g. filename)

>filename

Unzip tar.bz2 file (e.g. file.tar.bz2)

tar xvfj file.tar.bz2

Unzip tar.xz file (e.g. file.tar.xz)

unxz file.tar.xz tar xopf file.tar

Output a y/n repeatedly until killed

# 'y': yes # or 'n': yes n # or 'anything': yes anything # For example: ```bash 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 # or dd if=/dev/zero of=//dev/shm/200m bs=1M count=200 # Standard output: # 200+0 records in # 200+0 records out # 209715200 bytes (210 MB) copied, 0.0955679 s, 2.2 GB/s

Cat to a file

cat >myfile let me add sth here exit by control + c ^C

Keep /repeatedly executing the same command (e.g Repeat 'wc -l filename' every 1 second)

watch -n 1 wc -l filename

Print commands and their arguments when execute (e.g. echo `expr 10 + 20` )

set -x; echo `expr 10 + 20 `

Print some meaningful sentences to you (install fortune first)

fortune

Colorful (and useful) version of top (install htop first)

htop

Press any key to continue

read -rsp $'Press any key to continue...\n' -n1 key

Run sql-like command on files from terminal

# download: # https://github.com/harelba/q # example: q -d "," "select c3,c4,c5 from /path/to/file.txt where c3='foo' and c5='boo'"

Using Screen for multiple terminal sessions

# Create session and attach: screen # Create detached session foo: screen -S foo -d -m # Detached session foo: screen: ^a^d # List sessions: screen -ls # Attach last session: screen -r # Attach to session foo: screen -r foo # Kill session foo: screen -r foo -X quit # Scroll: Hit your screen prefix combination (C-a / control+A), then hit Escape. Move up/down with the arrow keys (↑ and ↓). # Redirect output of an already running process in Screen: (C-a / control+A), then hit 'H' # Store screen output for Screen: Ctrl+A, Shift+H # You will then find a screen.log file under current directory.

Using Tmux for multiple terminal sessions

# Create session and attach: tmux # Attach to session foo: tmux attach -t foo # Detached session foo: ^bd # List sessions: tmux ls # Attach last session: tmux attach # Kill session foo: tmux kill-session -t foo # Create detached session foo: tmux new -s foo -d # Send command to all panes in tmux: Ctrl-B :setw synchronize-panes # Some tmux pane control commands: Ctrl-B # Panes (splits), Press Ctrl+B, then input the following symbol: # % horizontal split # " vertical split # o swap panes # q show pane numbers # x kill pane # space - toggle between layouts # Distribute Vertically (rows): select-layout even-vertical # or Ctrl+b, Alt+2 # Distribute horizontally (columns): select-layout even-horizontal # or Ctrl+b, Alt+1 # Scroll Ctrl-b then \[ then you can use your normal navigation keys to scroll around. Press q to quit scroll mode.

Cut the last column

cat filename|rev|cut -f1|rev

Pass password to ssh

sshpass -p mypassword ssh root@10.102.14.88 "df -h"

Wait for a pid (job) to complete

wait %1 # or wait $PID wait ${!} #wait ${!} to wait till the last background process ($! is the PID of the last background process)

Convert pdf to txt

sudo apt-get install poppler-utils pdftotext example.pdf example.txt

List only directory

ls -ld -- */

Capture/record/save terminal output (capture everything you type and output)

script output.txt # start using terminal # to logout the screen session (stop saving the contents), type exit.

List contents of directories in a tree-like format.

tree # go to the directory you want to list, and type tree (sudo apt-get install tree) # output: # 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

# 1. install virtualenv. sudo apt-get install virtualenv # 2. Create a directory (name it .venv or whatever name your want) for your new shiny isolated environment. virtualenv .venv # 3. source virtual bin source .venv/bin/activate # 4. you can check check if you are now inside a sandbox. type pip # 5. Now you can install your pip package, here requirements.txt is simply a txt file containing all the packages you want. (e.g tornado==4.5.3). pip install -r requirements.txt

Working with json data

#install the useful jq package #sudo apt-get install jq #e.g. to get all the values of the 'url' key, simply pipe the json to the following jq command(you can use .[]. to select inner json, i.e jq '.[].url') jq '.url'

Editing your history

history -w vi ~/.bash_history history -r

Decimal to Binary (e.g get binary of 5)

D2B=({0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}{0..1}) echo -e ${D2B[5]} #00000101 echo -e ${D2B[255]} #11111111

Wrap each input line to fit in specified width (e.g 4 integers per line)

echo "00110010101110001101" | fold -w4 # 0011 # 0010 # 1011 # 1000 # 1101

Sort a file by column and keep the original order

sort -k3,3 -s

Right align a column (right align the 2nd column)

cat file.txt|rev|column -t|rev

To both view and store the output

echo 'hihihihi' | tee outputfile.txt # use '-a' with tee to append to file.

Show non-printing (Ctrl) characters with cat

cat -v filename

Convert tab to space

expand filename

Convert space to tab

unexpand filename

Display file in octal ( you can also use od to display hexadecimal, decimal, etc)

od filename

Reverse cat a file

tac filename

Reverse the result from `uniq -c`

while read a b; do yes $b |head -n $a ;done <test.txt

More coming!!

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CODE_OF_CONDUCT.md		CODE_OF_CONDUCT.md
LICENSE		LICENSE
README.md		README.md
_config.yml		_config.yml

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Bash-Oneliner

Handy Bash one-liners

Terminal Tricks

Using Ctrl keys

Change case

Run history number (e.g. 53)

Run last command

Run last command and change some parameter using caret substitution (e.g. last command: echo 'aaa' -> rerun as: echo 'bbb')

Run past command that began with (e.g. cat filename)

Bash globbing

Some handy environment variables

Grep

Type of grep

Grep and count number of empty lines

Grep and return only integer

Grep integer with certain number of digits (e.g. 3)

Grep only IP address

Grep whole word (e.g. 'target')

Grep returning lines before and after match (e.g. 'bbo')

Grep string starting with (e.g. 'S')

Extract text between words (e.g. w1,w2)

Grep lines without word (e.g. bbo)

Grep lines not begin with string (e.g. #)

Grep variables with space within it (e.g. bbo="some strings")

Grep only one/first match (e.g. bbo)

Grep and return number of matching line(e.g. bbo)

Count occurrence (e.g. three times a line count three times)

Case insensitive grep (e.g. bbo/BBO/Bbo)

COLOR the match (e.g. bbo)!

Grep search all files in a directory(e.g. bbo)

Search all files in directory, do not ouput the filenames (e.g. bbo)

Search all files in directory, output ONLY the filenames with matches(e.g. bbo)

Grep OR (e.g. A or B or C or D)

Grep AND (e.g. A and B)

Regex any singer character (e.g. ACB or AEB)

Regex with or without a certain character (e.g. color or colour)

Grep all content of a fileA from fileB

Grep a tab

Grep variable from variable

Grep strings between a bracket()

Grep number of characters with known strings in between(e.g. AAEL000001-RA)

Skip directory (e.g. bbo)

Sed

Remove the 1st line

Remove the first 100 lines (remove line 1-100)

Remove lines with string (e.g. bbo)

Remove lines whose nth character not equal to a value (e.g. 5th character not equal to 2)

Edit infile (edit and save)

When using variable (e.g. $i), use double quotes " "

Using environment variable and end-of-line pattern at the same time.

Delete/remove empty lines

Delete/remove last line

Delete/remove last character from end of file

Add string to beginning of file (e.g. "[")

Add string at certain line number (e.g. add 'something' to line 1 and line 3)

Add string to end of file (e.g. "]")

Add newline to the end

Add string to beginning of every line (e.g. bbo)

Add string to end of each line (e.g. "}")

Add \n every nth character (e.g. every 4th character)

Concatenate/combine/join files with a seperator and next line (e.g separate by ",")

Substitution (e.g. replace A by B)

Substitution with wildcard (e.g. replace a line start with aaa= by aaa=/my/new/path)

Select lines start with string (e.g. bbo)

Delete lines with string (e.g. bbo)

Print/get/trim a range of line (e.g. line 500-5000)

Print every nth lines

Print every odd # lines

Print every third line including the first line

Remove leading whitespace and tabs

Remove only leading whitespace

Remove ending commas

Add a column to the end

Add extension of filename to last column

Remove newline\ nextline

Print a particular line (e.g. 123th line)