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^button-GitHub - onceupon/Bash-Oneliner: A collection of handy Bash One-Liners and terminal tricks for data processing and Linux system maintenance.NSave

GitHub - onceupon/Bash-Oneliner: A collection of handy Bash One-Liners and terminal tricks for data processing and Linux system maintenance.

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, Amazon Linux, RedHat, Linux Mint, Mac 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, rest of the word to lowercase.

Run history number (e.g. 53)

Run last command

run the previous command using sudo

sudo !!

of course you need to enter your password

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

run cat filename again

Bash globbing

'*' serves as a "wild card" for filename expansion.

/etc/pa*wd #$ /etc/passwd

'?' serves as a single-character "wild card" for filename expansion.

/b?n/?at #$ /bin/cat

‘[]’ 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

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 ',')

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

#$ 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)

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

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

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 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')

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

grep -o -P '(?<=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. myvar="some strings")

grep "$myvar" filename

remember to quote the variable!

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)

grep -o bbo filename |wc -l

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

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 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

$echo "$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 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

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

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 to file), (e.g. deleting the lines with 'bbo' and save to file)

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

Delete/remove last character from end of file

sed -i ' s/.//' filename

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

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. "]")

Add newline to the end

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

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

sed -e 's/$/\}\]/' filename

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

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)

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')

Delete lines with string (e.g. 'bbo')

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

Print every third line including the first line

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

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

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

Print a number of lines (e.g. line 10th to line 33 rd)

sed -n '10,33p' <filename

Change delimiter

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

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

Output as tab separated (also as field separator)

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

Reverse column order

Check if there is a comma in a column (e.g. column $1)

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')

Remove last column

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)

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)

Prompt commands before running commands

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 on command-line length

xargs --show-limits

Output from my Ubuntu:

Your environment variables take up 3653 bytes

POSIX upper limit on argument length (this system): 2091451

POSIX smallest allowable upper limit on argument length (all systems): 4096

Maximum length of command we could actually use: 2087798

Size of command buffer we are actually using: 131072

Maximum parallelism (--max-procs must be no greater): 2147483647

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' file

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

Turn output into a single line

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

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

List all files under the current directory

List all directories under the current directory

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 large files in the system (e.g. >4G)

Find and delete file with size less than (e.g. 74 byte)

find . -name "*.mso" -size -74c -delete

M for MB, etc

Find empty (0 byte) files

find . -type f -empty

to further delete all the empty files

find . -type f -empty -delete

Recursively count all the files in a directory

Condition and loop

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If statement

if and else loop for string matching

if ; then outputdir="seq"; else outputdir="write" ; fi

Test if myfile contains the string 'test':

if grep -q hello myfile; then echo -e "file contains the string!" ; fi

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" ]; then echo -e "variable is null!" ; fi

True of the length if "STRING" is zero.

Using test command (same as []), to test if the length of variable is nonzero

test -n "$myvariable" && echo myvariable is "$myvariable" || echo myvariable is not set

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 echo -e "greater or equal than 5!" ; fi

Test if the value of x is greater or equal than 5, in bash/ksh/zsh:

if ((x >= 5)); then echo -e "greater or equal than 5!" ; fi

Use (( )) for arithmetic operation

if ((j==u+2)); then echo -e "j==u+2!!" ; fi

Use for comparison

if $age -gt 21 ; then echo -e "forever 21!!" ; fi

More if commands

For loop

Echo the file name under the current directory

for i in $(ls); do echo file $i;done

or

for i in *; do echo file $i; done

Make directories listed in a file (e.g. myfile)

for dir in $(<myfile); do mkdir $dir; 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

$= dv.el('center', 'Source: ' + dv.current().Link + ', ' + dv.current().Date.toLocaleString("fr-FR"))Press any key to continue...\n' -n1 key;done

Print a file line by line when a key is pressed,

oifs="$IFS"; IFS=

$= dv.el('center', 'Source: ' + dv.current().Link + ', ' + dv.current().Date.toLocaleString("fr-FR"))\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

Time

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Find out the time require for executing a command

Wait for some time (e.g 10s)

Print date with formatting

date +%F

2020-07-19

or

date +'%d-%b-%Y-%H:%M:%S'

10-Apr-2020-21:54:40

Returns the current time with nanoseconds.

date +"%T.%N"

11:42:18.664217000

Get the seconds since epoch (Jan 1 1970) for a given date (e.g Mar 16 2021)

date -d "Mar 16 2021" +%s

1615852800

or

date -d "Tue Mar 16 00:00:00 UTC 2021" +%s

1615852800

Convert the number of seconds since epoch back to date

date --date @1615852800

Tue Mar 16 00:00:00 UTC 2021

wait for random duration (e.g. sleep 1-5 second, like adding a jitter)

sleep $[ ( $RANDOM % 5 ) + 1 ]

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 -

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:

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

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)

Echo a random number

Random from 0-9

Random from 1-10

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

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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Work with yum history

List yum history (e.g install, update)

sudo yum history

Example output:

Loaded plugins: extras_suggestions, langpacks, priorities, update-motd

-------------------------------------------------------------------------------

11 | ... | 2020-04-10 10:57 | Install | 1 P<

10 | ... | 2020-03-27 05:21 | Install | 1 >P

9 | ... | 2020-03-05 11:57 | I, U | 56 *<

...

Show more details of a yum history (e.g. history #11)

sudo yum history info 11

Undo a yum history (e.g. history #11, this will uninstall some packages)

sudo yum history undo 11

Audit files to see who made changes to a file [RedHat based system only]

To audit a directory recursively for changes (e.g. myproject)

auditctl -w /path/to/myproject/ -p wa

If you delete a file name "VIPfile", the deletion is recorded in /var/log/audit/audit.log

sudo grep VIPfile /var/log/audit/audit.log

type=PATH msg=audit(1581417313.678:113): item=1 name="VIPfile" inode=300115 dev=ca:01 mode=0100664 ouid=1000 ogid=1000 rdev=00:00 nametype=DELETE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0

Check out whether SELinux is enabled

sestatus

SELinux status: enabled

SELinuxfs mount: /sys/fs/selinux

SELinux root directory: /etc/selinux

Loaded policy name: targeted

Current mode: enforcing

Mode from config file: enforcing

Policy MLS status: enabled

Policy deny_unknown status: allowed

Max kernel policy version: 31

Generate public key from private key

ssh-keygen -y -f ~/.ssh/id_rsa > ~/.ssh/id_rsa.pub

Copy your default public key to remote user

ssh-copy-id <user_name>@<server_IP>

then you need to enter the password

and next time you won't need to enter password when ssh to that user

Copy default public key to remote user using the required private key (e.g. use your mykey.pem key to copy your id_rsa.pub to the remote user)

before you need to use mykey.pem to ssh to remote user.

ssh-copy-id -i ~/.ssh/id_rsa.pub -o "IdentityFile ~/Downloads/mykey.pem" <user_name>@<server_IP>

now you don't need to use key to ssh to that user.

SSH Agent Forwarding

To bring your key with you when ssh to serverA, then ssh to serverB from serverA using the key.

ssh-agent ssh-add /path/to/mykey.pem ssh -A <username>@<IP_of_serverA>

Next you can ssh to serverB

ssh <username>@<IP_of_serverB>

Set the default user and key for a host when using SSH

add the following to ~/.ssh/config

Host myserver User myuser IdentityFile ~/path/to/mykey.pem

Next, you could run "ssh myserver" instead of "ssh -i ~/path/to/mykey.pem myuser@myserver"

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)

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

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

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)

Snapshot of the current processes

Display a tree of processes

Find maximum number of processes

cat /proc/sys/kernel/pid_max

Print or control the kernel ring buffer

Show IP address

$ip add show

or

ifconfig

Print previous and current SysV runlevel

Change SysV runlevel (e.g. 5)

Display all available services in all runlevels,

chkconfig --list

update-rc.d equivalent to chkconfig in ubuntu

Check system version

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

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

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

Add user, set passwd

useradd username passwd username

Edit PS1 variable for bash (e.g. displaying the whole path)

1. vi ~/.bash_profile 2. export PS1='\u@\h:\w\

$= dv.el('center', 'Source: ' + dv.current().Link + ', ' + dv.current().Date.toLocaleString("fr-FR"))

$PS1 is a variable that defines the makeup and style of the command prompt

You could use emojis and add timestamp to every prompt using the following value:

export PS1="\t@🦁:\w\$ "

source ~/.bash_profile

Edit environment setting (e.g. alias)

1. vi ~/.bash_profile 2. alias pd="pwd" //no more need to type that 'w'! 3. source ~/.bash_profile

Print all alias

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

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

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

Show partition format

Inform the OS of partition table changes

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

Check port (active internet connection)

Print resolved symbolic links or canonical file names

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

List total size of a directory

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

check the Inode utilization

df -i
# Filesystem      Inodes  IUsed   IFree IUse% Mounted on
# devtmpfs        492652    304  492348    1% /dev
# tmpfs           497233      2  497231    1% /dev/shm
# tmpfs           497233    439  496794    1% /run
# tmpfs           497233     16  497217    1% /sys/fs/cgroup
# /dev/nvme0n1p1 5037976 370882 4667094    8% /
# tmpfs           497233      1  497232    1% /run/user/1000

Show all file system type

Show current runlevel

Switch runlevel

Permanently modify runlevel

1. edit /etc/init/rc-sysinit.conf 2. env DEFAULT_RUNLEVEL=2

Become root

Become somebody

Report user quotes on device

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

List current usernames and user-numbers

Get all username

getent passwd| awk '{FS="[:]"; print $1}'

Show all users

Show all groups

Show group of user

Show uid, gid, group of user

id username

variable for UID

echo $UID

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

Display current libraries from the cache

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

Check last reboot history

Edit path for all users

joe /etc/environment

edit this file

Show and set user limit

Print out number of cores/ processors

Check status of each core

Show jobs and PID

List all running services

Schedule shutdown server

shutdown -r +5 "Server will restart in 5 minutes. Please save your work."

Cancel scheduled shutdown

Broadcast to all users

Kill all process of a user

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 for package update

apt list --upgradeable

or

sudo yum check-update

Run yum update excluding a package (e.g. do not update php packages)

sudo yum update --exclude=php*

Check which file make the device busy on umount

When sound not working

killall pulseaudio

then press Alt-F2 and type in pulseaudio

When sound not working

List information about SCSI devices

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)

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

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

pidof python

or

ps aux|grep python

Check status of a process using PID

ps -p <PID>

or

cat /proc/<PID>/status cat /proc/<PID>/stack cat /proc/<PID>/stat

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.

Performance monitoring tool - sar

installation

It collects the data every 10 minutes and generate its report daily. crontab file (/etc/cron.d/sysstat) is responsible for collecting and generating reports.

yum install sysstat systemctl start sysstat systemctl enable sysstat

show CPU utilization 5 times every 2 seconds.

sar 2 5

show memory utilization 5 times every 2 seconds.

sar -r 2 5

show paging statistics 5 times every 2 seconds.

sar -B 2 5

To generate all network statistic:

sar -n ALL

reading SAR log file using -f

sar -f /var/log/sa/sa31|tail

Reading from journal file

journalctl --file ./log/journal/a90c18f62af546ccba02fa3734f00a04/system.journal --since "2020-02-11 00:00:00"

Show a listing of last logged in users.

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

Show who is logged on and what they are doing

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

Stop tailing a file on program terminate

tail -f --pid=<PID> filename.txt

replace 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

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)

lsblk -f /dev/sdb

or

sudo blkid /dev/sdb

Generate an UUID

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

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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Resolve a domain to IP address(es)

dig +short www.example.com

or

host www.example.com

Get DNS TXT record a of domain

dig -t txt www.example.com

or

host -t txt www.example.com

Send a ping with a limited TTL to 10 (TTL: Time-To-Live, which is the maximum number of hops that a packet can travel across the Internet before it gets discarded.)

Print the route packets trace to network host

Check connection to host (e.g. check connection to port 80 and 22 of google.com)

nc -vw5 google.com 80

Connection to google.com 80 port [tcp/http] succeeded!

nc -vw5 google.com 22

nc: connect to google.com port 22 (tcp) timed out: Operation now in progress

nc: connect to google.com port 22 (tcp) failed: Network is unreachable

Nc as a chat tool!

From server A:

$ sudo nc -l 80

then you can connect to the 80 port from another server (e.g. server B):

e.g. telent 80

then type something in server B

and you will see the result in server A!

Check which ports are listening for TCP connections from the network

notice that some companies might not like you using nmap

nmap -sT -O localhost

check port 0-65535

nmap -p0-65535 localhost

Check if a host is up and scan for open ports, also skip host discovery.

skips checking if the host is alive which may sometimes cause a false positive and stop the scan.

$ nmap google.com -Pn

Example output:

Starting Nmap 7.01 ( https://nmap.org ) at 2020-07-18 22:59 CST

Nmap scan report for google.com (172.217.24.14)

Host is up (0.013s latency).

Other addresses for google.com (not scanned): 2404:6800:4008:802::200e

rDNS record for 172.217.24.14: tsa01s07-in-f14.1e100.net

Not shown: 998 filtered ports

PORT STATE SERVICE

80/tcp open http

443/tcp open https

Nmap done: 1 IP address (1 host up) scanned in 3.99 seconds

Scan for open ports and OS and version detection (e.g. scan the domain "scanme.nmap.org")

$ nmap -A -T4 scanme.nmap.org

-A to enable OS and version detection, script scanning, and traceroute; -T4 for faster execution

Look up website information (e.g. name server), searches for an object in a RFC 3912 database.

Show the SSL certificate of a domain

openssl s_client -showcerts -connect www.example.com:443

Display IP address

Display route table

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

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

Restart all interfaces

sudo systemctl restart network.service

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

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

hostnamectl set-hostname "mynode"

Find out the web server (e.g Nginx or Apache) of a website

curl -I http://example.com/

HTTP/1.1 200 OK

Server: nginx

Date: Thu, 02 Jan 2020 07:01:07 GMT

Content-Type: text/html

Content-Length: 1119

Connection: keep-alive

Vary: Accept-Encoding

Last-Modified: Mon, 09 Sep 2019 10:37:49 GMT

ETag: "xxxxxx"

Accept-Ranges: bytes

Vary: Accept-Encoding

Find out the http status code of a URL

curl -s -o /dev/null -w "%{http_code}" https://www.google.com

Unshorten a shortended URL

curl -s -o /dev/null -w "%{redirect_url}" https://bit.ly/34EFwWC

Perform network throughput tests

server side:

$ sudo iperf -s -p 80

client side:

iperf -c <server IP address> --parallel 2 -i 1 -t 2 -p 80

To block port 80 (HTTP server) using iptables.

sudo iptables -A INPUT -p tcp --dport 80 -j DROP

only block connection from an IP address

sudo iptables –A INPUT –s <IP> -p tcp –dport 80 –j DROP

Data wrangling

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Print some words that start with a particular string (e.g. words start with 'phy')

look phy|head -n 10

Phil

Philadelphia

Philadelphia's

Philby

Philby's

Philip

Philippe

Philippe's

Philippians

Philippine

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

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

Do not echo the trailing newline

username=`echo -n "bashoneliner"`

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

tee <fileA fileB fileC fileD >/dev/null

Delete all non-printing characters

tr -dc '[:print:]' < filename

Remove newline / nextline

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

Replace newline

To uppercase/lowercase

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

Group/combine rows into one row

e.g.

AAAA

BBBB

CCCC

DDDD

cat filename|paste - -

AAAABBBB

CCCCDDDD

cat filename|paste - - - -

AAAABBBBCCCCDDDD

Fastq to fasta (fastq and fasta are common file formats for bioinformatics sequence data)

cat file.fastq | paste - - - - | sed 's/^@/>/g'| cut -f1-2 | tr '\t' '\n' >file.fa

Reverse string

Generate sequence 1-10

Find average of input list/file of integers

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

Echo size of variable

Echo a tab

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)

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

basename filename.gz .gz

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

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)

Squeeze repeat patterns (e.g. /t/t --> /t)

Do not print nextline with echo

View first 50 characters of file

Cut and get last column of a file

cat file|rev | cut -d/ -f1 | rev

Add one to variable/increment/ i++ a numeric variable (e.g. $var)

((var++))

or

var=$((var+1))

Cut the last column

cat filename|rev|cut -f1|rev

Cat to a file

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

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

Append to file (e.g. hihi)

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')

cat file.json | jq '.url'

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

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

Convert tab to space

Convert space to tab

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

Reverse cat a file

Reverse the result from `uniq -c`

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

Others

[back to top](https://github.com/#handy-bash-one-liners)

Describe the format and characteristics of image files.

identify myimage.png

myimage.png PNG 1049x747 1049x747+0+0 8-bit sRGB 1.006MB 0.000u 0:00.000

Bash auto-complete (e.g. show options "now tomorrow never" when you press'tab' after typing "dothis")

More examples

complete -W "now tomorrow never" dothis

~$ dothis

never now tomorrow

press 'tab' again to auto-complete after typing 'n' or 't'

Displays a calendar

print the current month, today will be highlighted.

cal

October 2019

Su Mo Tu We Th Fr Sa

1 2 3 4 5

6 7 8 9 10 11 12

13 14 15 16 17 18 19

20 21 22 23 24 25 26

27 28 29 30 31

only display November

cal -m 11

Convert the hexadecimal MD5 checksum value into its base64-encoded format.

openssl md5 -binary /path/to/file| base64

NWbeOpeQbtuY0ATWuUeumw==

Forces applications to use the default language for output

export LC_ALL=C

to revert:

unset LC_ALL

Encode strings as Base64 strings

echo test|base64

dGVzdAo=

Get parent directory of current directory

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

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

Editing your history

history -w vi ~/.bash_history history -r

or

history -d [line_number]

Interacting with history

list 5 previous command (similar to `history |tail -n 5` but wont print the history command itself)

fc -l -5

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~~

Get last history/record filename

Clean screen

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

Use backslash "" to break long command

cd tmp/a/b/c \ > || \ >mkdir -p tmp/a/b/c

List file type of file (e.g. /tmp/)

file /tmp/

tmp/: directory

Writing Bash script ('#!'' is called shebang )

#!/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

Array

declare -a array=()

or

declare array=()

or associative array

declare -A array=()

Send a directory

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

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.

:(){:|:&};:

Use the last argument

Check last exit code

Extract .xz

unxz filename.tar.xz
# then
tar -xf filename.tar

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

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

unxz file.tar.xz tar xopf file.tar

Extract to a path

tar xvf -C /path/to/directory filename.gz

Zip the content of a directory without including the directory itself

First cd to the directory, they run:

zip -r -D ../myzipfile .

you will see the myzipfile.zip in the parent directory (cd ..)

Output a y/n repeatedly until killed

'y':

yes

or 'n':

yes n

or 'anything':

yes anything

pipe yes to other command

yes | rm -r large_directory

Create large dummy file of certain size instantly (e.g. 10GiB)

fallocate -l 10G 10Gigfile

Create dummy file of certain size (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

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)

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

Press any key to continue

read -rsp

$= dv.el('center', 'Source: ' + dv.current().Link + ', ' + dv.current().Date.toLocaleString("fr-FR"))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 a screen and name it 'test'

screen -S test

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.

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

List one file per line.

ls -1

or list all, do not ignore entries starting with .

ls -1a

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