# Bash-Oneliner I am glad that you are here! I started working on bioinformatics four years ago (recently switched to cloud computing), and was amazed by those single-word bash commands which are much faster than my dull scripts, so much time can be saved through knowing command-line shortcuts and scripting. Not all the code here is oneliner (if the ';' counts..), but i put effort on making them brief and fast. I am mainly using Ubuntu, RedHat and Linux Mint, sorry if the commands dont work on your system. This blog will focus on simple bash commands for parsing data; some of them are for Linux system maintenance i acquired from work and when i was studying LPIC (I have LPIC1 certificate now ^^). 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, so... correct me anytime, thank you! And if you know any cool command that are not included here, Please Teach Me. In case you would like to check and vote up my questions on Stackoverflow, here's my page: http://stackoverflow.com/users/4290753/once Here's a more stylish version of Bash-Oneliner~ http://onceupon.github.io/Bash-Oneliner/ ## Handy Bash oneliner commands - [Terminal Tricks](#terminal-tricks) - [Variable](#variable) - [Grep](#grep) - [Sed](#sed) - [Awk](#awk) - [Xargs](#xargs) - [Find](#find) - [Loops](#loops) - [Math](#math) - [Time](#time) - [Download](#download) - [Random](#random) - [Xwindow](#xwindow) - [System](#system) - [Hardware](#hardware) - [Others](#others) ## Terminal Tricks ##### Ctrl ```bash Ctrl + n : same as Down arrow. Ctrl + p : same as Up arrow. Ctrl + r : begins a backward search through cammand 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 + x + Ctrl + e : launch editor define by $EDITOR ``` ##### Change case ```bash 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 uppercase. Esc + c # converts letter under the cursor to uppercase. ``` ##### Run history number (e.g. 53) ```bash !53 ``` ##### Run last command ```bash !! ``` ##### Run last command and change some parameter (e.g. last command: echo 'aaa' -> rerun as: echo 'bbb') ```bash #last command: echo 'aaa' ^aaa^bbb #echo 'bbb' #bbb ``` ##### Run past command that began with (e.g. cat filename) ```bash !cat ``` or ```bash !c # run cat filename again ``` ## Grep [[back to top](#handy-bash-oneliner-commands)] ##### Type of grep ```bash 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 return only integer ```bash grep -o '[0-9]*' #or grep -oP '\d' ``` ##### Grep integer with certain number of digits (e.g. 3) ```bash grep ‘[0-9]\{3\}’ # or grep -E ‘[0-9]{3}’ # or grep -P ‘\d{3}’ ``` ##### Grep only IP address ```bash 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') ```bash grep -w 'target' #or using RE grep '\btarget\b' ``` ##### Grep returning lines before and after match (e.g. 'bbo') ```bash # 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') ```bash grep -o 'S.*' ``` ##### Extract text bewteen words (e.g. w1,w2) ```bash grep -o -P '(?<=w1).*(?=w2)' ``` ##### Grep lines without word (e.g. bbo) ```bash grep -v bbo filename ``` ##### Grep lines not begin with string (e.g. #) ```bash grep -v '^#' file.txt ``` ##### Grep variables with space within it (e.g. bbo="some strings") ```bash grep "$boo" filename ``` #remember to quote the variable! ##### Grep only one/first match (e.g. bbo) ```bash grep -m 1 bbo filename ``` ##### Grep and return number of matching line(e.g. bbo) ```bash grep -c bbo filename ``` ##### Count occurrence (e.g. three times a line count three times) ```bash grep -o bbo filename |wc -l ``` ##### Case insensitive grep (e.g. bbo/BBO/Bbo) ```bash grep -i "bbo" filename ``` ##### COLOR the match (e.g. bbo)! ```bash grep --color bbo filename ``` ##### Grep search all files in a directory(e.g. bbo) ```bash grep -R bbo /path/to/directory ``` or ```bash grep -r bbo /path/to/directory ``` ##### Search all files in directory, do not ouput the filenames (e.g. bbo) ```bash grep -rh bbo /path/to/directory ``` ##### Search all files in directory, output ONLY the filenames with matches(e.g. bbo) ```bash 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) ```bash grep 'A.*B' ``` ##### Regex any singer character (e.g. ACB or AEB) ```bash grep 'A.B' ``` ##### Regex with or without a certain character (e.g. color or colour) ```bash grep ‘colou?r’ ``` ##### Grep all content of a fileA from fileB ```bash grep -f fileA fileB ``` ##### Grep a tab ```bash grep $'\t' ``` ##### Grep variable from variable ```bash $echo "$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() ```bash grep -oP '\(\K[^\)]+' ``` ##### Grep number of characters with known strings in between(e.g. AAEL000001-RA) ```bash grep -o -w "\w\{10\}\-R\w\{1\}" # \w word character [0-9a-zA-Z_] \W not word character ``` ##### Skip directory (e.g. bbo) ```bash grep -d skip 'bbo' /path/to/files/* ``` ## Sed [[back to top](#handy-bash-oneliner-commands)] ##### Remove the 1st line ```bash sed 1d filename ``` ##### Remove the first 100 lines (remove line 1-100) ```bash sed 1,100d filename ``` ##### Remove lines with string (e.g. bbo) ```bash 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) ```bash sed -E '/^.{5}[^2]/d' #aaaa2aaa (you can stay) #aaaa1aaa (delete!) ``` ##### Edit infile (edit and save) ```bash sed -i "/bbo/d" filename ``` ##### When using variable (e.g. $i), use double quotes " " e.g. add >$i to the first line (to make a FASTA file) ```bash sed "1i >$i" # notice the double quotes! in other examples, you can use a single quote, but here, no way! # '1i' means insert to first line ``` ##### Delete/remove empty lines ```bash sed '/^\s*$/d' ``` or ```bash sed '/^$/d' ``` ##### Delete/remove last line ```bash sed '$d' ``` ##### Delete/remove last character from end of file ```bash sed -i '$ s/.$//' filename ``` ##### Add string to beginning of file (e.g. "\[") ```bash sed -i '1s/^/[/' file ``` ##### Add string to end of file (e.g. "]") ```bash sed '$s/$/]/' filename ``` ##### Add newline to the end ```bash sed '$a\' ``` ##### Add string to beginning of every line (e.g. bbo) ```bash sed -e 's/^/bbo/' file ``` ##### Add string to end of each line (e.g. "}") ```bash sed -e 's/$/\}\]/' filename ``` ##### Add \n every nth character (e.g. every 4th character) ```bash sed 's/.\{4\}/&\n/g' ``` ##### Concatenate/combine/join files with a seperator and next line (e.g seperate by ",") ```bash sed -s '$a,' *.json > all.json ``` ##### Substitution (e.g. replace A by B) ```bash sed 's/A/B/g' filename ``` ##### Substitution with wildcard (e.g. replace a line start with aaa= by aaa=/my/new/path) ```bash sed "s/aaa=.*/aaa=\/my\/new\/path/g" ``` ##### Select lines start with string (e.g. bbo) ```bash sed -n '/^@S/p' ``` ##### Delete lines with string (e.g. bbo) ```bash sed '/bbo/d' filename ``` ##### Print/get/trim a range of line (e.g. line 500-5000) ```bash sed -n 500,5000p filename ``` ##### Print every nth lines ```bash sed -n '0~3p' filename # catch 0: start; 3: step ``` ##### Print every odd # lines ```bash sed -n '1~2p' ``` ##### Print every third line including the first line ```bash sed -n '1p;0~3p' ``` ##### Remove leading whitespace and tabs ```bash sed -e 's/^[ \t]*//' ``` //notice a whitespace before '\t'!! ##### Remove only leading whitespace ```bash sed 's/ *//' # notice a whitespace before '*'!! ``` ##### Remove ending commas ```bash sed 's/,$//g' ``` ##### Add a column to the end ```bash sed "s/$/\t$i/" # $i is the valuable you want to add # e.g. add the filename to every last column of the file ``` ```bash for i in $(ls);do sed -i "s/$/\t$i/" $i;done ``` ##### Add extension of filename to last column ```bash for i in T000086_1.02.n T000086_1.02.p;do sed "s/$/\t${i/*./}/" $i;done >T000086_1.02.np ``` ##### Remove newline\ nextline ```bash sed ':a;N;$!ba;s/\n//g' ``` ##### Print a particular line (e.g. 123th line) ```bash sed -n -e '123p' ``` ##### Print a number of lines (e.g. line 10th to line 33 rd) ```bash sed -n '10,33p' AAA#AAA) ```bash sed -r -e 's/^.{3}/&#/' file ``` ## Awk [[back to top](#handy-bash-oneliner-commands)] ##### Set tab as field separator ```bash awk -F $'\t' ``` ##### Output as tab separated (also as field separator) ```bash awk -v OFS='\t' ``` ##### Pass variable ```bash a=bbo;b=obb; awk -v a="$a" -v b="$b" "$1==a && $10=b" filename ``` ##### Print line number and number of characters on each line ```bash awk '{print NR,length($0);}' filename ``` ##### Find number of columns ```bash awk '{print NF}' ``` ##### Reverse column order ```bash awk '{print $2, $1}' ``` ##### Check if there is a comma in a column (e.g. column $1) ```bash awk '$1~/,/ {print}' ``` ##### Split and do for loop ```bash awk '{split($2, a,",");for (i in a) print $1"\t"a[i]}' filename ``` ##### Print all lines before nth occurence of a string (e.g stop print lines when bbo appears 7 times) ```bash awk -v N=7 '{print}/bbo/&& --N<=0 {exit}' ``` ##### Print filename and last line of all files in directory ```bash 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) ```bash awk 'BEGIN{OFS="\t"}$3="chr"$3' ``` ##### Remove lines with string (e.g. bbo) ```bash awk '!/bbo/' file ``` ##### Remove last column ```bash awk 'NF{NF-=1};1' file ``` ##### Usage and meaning of NR and FNR e.g. fileA: a b c fileB: d e ```bash awk 'print FILENAME, NR,FNR,$0}' fileA fileB ``` fileA 1 1 a fileA 2 2 b fileA 3 3 c fileB 4 1 d fileB 5 2 e ##### AND gate e.g. fileA: 1 0 2 1 3 1 4 0 fileB: 1 0 2 1 3 0 4 1 ```bash 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) ```bash 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 ```bash awk '{printf("%s\t%s\n",NR,$0)}' ``` ##### Break combine column data into rows e.g. seperate David cat,dog into David cat David dog detail here:　http://stackoverflow.com/questions/33408762/bash-turning-single-comma-separated-column-into-multi-line-string ```bash awk '{split($2,a,",");for(i in a)print $1"\t"a[i]}' file ``` ##### Average a file (each line in file contains only one number) ```bash awk '{s+=$1}END{print s/NR}' ``` ##### Print field start with string (e.g Linux) ```bash awk '$1 ~ /^Linux/' ``` ##### Sort a row (e.g. 1 40 35 12 23 --> 1 12 23 35 40) ```bash 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) ```bash awk '{$6 = $4 - prev5; prev5 = $5; print;}' ``` ## Xargs [[back to top](#handy-bash-oneliner-commands)] ##### Set tab as delimiter (default:space) ```bash xargs -d\t ``` ##### Display 3 items per line ```bash echo 1 2 3 4 5 6| xargs -n 3 # 1 2 3 # 4 5 6 ``` ##### Prompt before execution ```bash echo a b c |xargs -p -n 3 ``` ##### Print command along with output ```bash xargs -t abcd # bin/echo abcd # abcd ``` ##### With find and rm ```bash find . -name "*.html"|xargs rm # when using a backtick rm `find . -name "*.html"` ``` ##### Delete fiels with whitespace in filename (e.g. "hello 2001") ```bash find . -name "*.c" -print0|xargs -0 rm -rf ``` ##### Show limits ```bash xargs --show-limits ``` ##### Move files to folder ```bash find . -name "*.bak" -print 0|xargs -0 -I {} mv {} ~/old ``` or ```bash find . -name "*.bak" -print 0|xargs -0 -I file mv file ~/old ``` ##### Move first 100th files to a directory (e.g. d1) ```bash ls |head -100|xargs -I {} mv {} d1 ``` ##### Parallel ```bash time echo {1..5} |xargs -n 1 -P 5 sleep ``` a lot faster than ```bash time echo {1..5} |xargs -n1 sleep ``` ##### Copy all files from A to B ```bash 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 ```bash ls |xargs -n1 -I file sed -i '/^Pos/d' filename ``` ##### Add the file name to the first line of file ```bash ls |sed 's/.txt//g'|xargs -n1 -I file sed -i -e '1 i\>file\' file.txt ``` ##### Count all files ```bash ls |xargs -n1 wc -l ``` ##### Turn output into a single line ```bash ls -l| xargs ``` ##### Count files within directories ```bash echo mso{1..8}|xargs -n1 bash -c 'echo -n "$1:"; ls -la "$1"| grep -w 74 |wc -l' -- # "--" signals the end of options and display further option processing ``` ##### Download dependencies files and install (e.g. requirements.txt) ```bash cat requirements.txt| xargs -n1 sudo pip install ``` ##### Count lines in all file, also count total lines ```bash ls|xargs wc -l ``` ##### Xargs and grep ```bash cat grep_list |xargs -I{} grep {} filename ``` ##### Xargs and sed (replace all old ip address with new ip address under /etc directory) ```bash grep -rl '192.168.1.111' /etc | xargs sed -i 's/192.168.1.111/192.168.2.111/g' ``` ## Find [[back to top](#handy-bash-oneliner-commands)] ##### List all sub directory/file in the current directory ```bash find . ``` ##### List all files under the current directory ```bash find . -type f ``` ##### List all directories under the current directory ```bash find . -type d ``` ##### Edit all files under current directory (e.g. replace 'www' with 'ww') ```bash find . name '*.php' -exec sed -i 's/www/w/g' {} \; ``` if no subdirectory ```bash replace "www" "w" -- * # a space before * ``` ##### Find and output only filename (e.g. "mso") ```bash find mso*/ -name M* -printf "%f\n" ``` ##### Find and delete file with size less than (e.g. 74 byte) ```bash find . -name "*.mso" -size -74c -delete # M for MB, etc ``` ## Loops [[back to top](#handy-bash-oneliner-commands)] ##### While loop, column subtraction of a file (e.g. a 3 columns file) ```bash while read a b c; do echo $(($c-$b));done < <(head filename) #there is a space between the two '<'s ``` ##### While loop, sum up column subtraction ```bash i=0; while read a b c; do ((i+=$c-$b)); echo $i; done < <(head filename) ``` ##### While loop, keep checking a running process (e.g. perl) and start another new process (e.g. python) immetiately after it. (BETTER use the wait command! Ctrl+F 'wait') ```bash while [[ $(pidof perl) ]];do echo f;sleep 10;done && python timetorunpython.py ``` ##### If loop ```bash # if and else loop for string matching if [[ "$c" == "read" ]]; then outputdir="seq"; else outputdir="write" ; fi ``` if (($j==$u+2)) #(( )) use for arithmetic operation ``` ```bash if [[$age >21]] #[[ ]] use for comparison ``` ##### Test if file exist ```bash if [ -e 'filename' ] then echo -e "file exists!" fi ``` ##### if else Test if file exist ```bash if [ -e $filename ]; then echo -e "file exists!"; else mkdir $filename; fi ``` ##### For loop ```bash for i in $(ls); do echo file $i;done ``` ##### for loop, press any key to continue each loop ```bash 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 ``` ##### for loop, print a file line by line when a key is pressed ```bash for line in $(cat myfile); do echo $line; read -n1; done ``` ##### switch (case in bash) ```bash read type; case $type in '0') echo 'how' ;; '1') echo 'are' ;; '2') echo 'you' ;; esac ``` ## Variable [[back to top](#handy-bash-oneliner-commands)] ##### variable substitution within quotes ```bash # foo=bar echo "'$foo'" #'bar' # double/single quotes around single quotes make the inner single quotes expand variables ``` ##### get the length of variable ```bash var="some string" echo ${#var} # 11 ``` ##### get the first character of the variable ```bash var="some string" echo ${var%%"${var#?}"} #s ``` ##### remove the first or last string from variable ```bash var="some string" echo ${var:2} #me string ``` ##### replacement (e.g. remove the first leading 0 ) ```bash var="0050" echo ${var[@]#0} #050 ``` ##### replacement (e.g. replace 'a' with ',') ```bash {var/a/,} ``` ##### replace all (e.g. replace all 'a' with ',') ```bash {var//a/,} ``` ```bash #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 lower case (Parameter Expansion) ```bash var=HelloWorld echo ${var,,} helloworld ``` ## Math [[back to top](#handy-bash-oneliner-commands)] ##### Print out the prime factors of a number (e.g. 50) ```bash factor 50 ``` ##### Sum up input list (e.g. seq 10) ```bash seq 10|paste -sd+|bc ``` ##### Sum up a file (each line in file contains only one number) ```bash awk '{s+=$1} END {print s}' filename ``` ##### Column subtraction ```bash cat file| awk -F '\t' 'BEGIN {SUM=0}{SUM+=$3-$2}END{print SUM}' ``` ##### Simple math with expr ```bash expr 10+20 #30 expr 10\*20 #600 expr 30 \> 20 #1 (true) ``` ##### More math with bc - Number of decimal digit/ significant figure ```bash echo "scale=2;2/3" | bc #.66 ``` - Exponent operator ```bash echo "10^2" | bc #100 ``` - Using variables ```bash echo "var=5;--var"| bc #4 ``` ## Time [[back to top](#handy-bash-oneliner-commands)] ##### Find out the time require for executing a command ```bash time echo hi ``` ##### Wait for some time (e.g 10s) ```bash sleep 10 ``` ##### Log out your account after a certain period of time (e.g 10 seconds) ```bash TMOUT=10 #once you set this variable, logout timer start running! ``` ##### Set how long you want to run a command ```bash #This will run the commmand 'sleep 10' for only 1 second. timeout 1 sleep 10 ``` ##### Set when you want to run a command (e.g 1 min from now) ```bash 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> # press Ctrl + D to exit job 1 at Wed Apr 18 11:16:00 2018 ``` ## Download [[back to top](#handy-bash-oneliner-commands)] ##### Download all from a page ```bash wget -r -l1 -H -t1 -nd -N -np -A mp3 -e robots=off http://example.com # -r: recursive and download all links on page # -l1: only one level link # -H: span host, visit other hosts # -t1: numbers of retries # -nd: don't make new directories, download to here # -N: turn on timestamp # -nd: no parent # -A: type (seperate by ,) # -e robots=off: ignore the robots.txt file which stop wget from crashing the site, sorry example.com ``` ##### Upload a file to web and download (https://transfer.sh/) --> upload: ```bash curl --upload-file ./filename.txt https://transfer.sh/filename.txt ``` (the above command will return a URL, e.g: https://transfer.sh/tG8rM/filename.txt) --> download: ```bash curl https://transfer.sh/tG8rM/filename.txt -o filename.txt ``` ##### Download file if necessary ```bash 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) ```bash wget -O filename "http://example.com" ``` ##### Wget files to a folder ```bash wget -P /path/to/directory "http://example.com" ``` ## Random [[back to top](#handy-bash-oneliner-commands)] ##### Random pick 100 lines from a file ```bash shuf -n 100 filename ``` ##### Random order (lucky draw) ```bash 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) ```bash shuf -i 0-100 -n 15 ``` ##### Echo a random number ```bash echo $RANDOM ``` ##### Random from 0-9 ```bash echo $((RANDOM % 10)) ``` ##### Random from 1-10 ```bash echo $(((RANDOM %10)+1)) ``` ## Xwindow [[back to top](#handy-bash-oneliner-commands)] 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 ```bash 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 ```bash xclock xeyes xcowsay ``` ##### Open pictures/images from ssh server ```bash 1. ssh -X user_name@ip_address 2. apt-get install eog 3. eog picture.png ``` ##### Use gedit on server (GUI editor) ```bash 1. ssh -X user_name@ip_address 2. apt-get install gedit 3. gedit filename.txt ``` ##### Open PDF file from ssh server ```bash 1. ssh -X user_name@ip_address 2. apt-get install evince 3. evince filename.pdf ``` ##### Use google-chrome browser from ssh server ```bash 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 [[back to top](#handy-bash-oneliner-commands)] ##### Snapshot of the current processes ```bash ps ``` ##### Check graphics card ```bash lspci ``` ##### Show IP address ```bash $ip add show ``` or ```bash ifconfig ``` ##### Check system version ```bash cat /etc/*-release ``` ##### Linux Programmer's Manuel: hier- description of the filesystem hierarchy ```bash man hier ``` ##### List job ```bash jobs -l ``` ##### Export PATH ```bash export PATH=$PATH:~/path/you/want ``` ##### Make file execuable ```bash chmod +x filename # you can now ./filename to execute it ``` ##### Check system (x86-64) ```bash uname -i ``` ##### Surf the net ```bash links www.google.com ``` ##### Add user, set passwd ```bash useradd username passwd username ``` ##### Edit variable for bash, (e.g. displaying the whole path) ```bash 1. joe ~/.bash_profile 2. export PS1='\u@\h:\w\$' # $PS1 is a variable that defines the makeup and style of the command prompt ``` ```bash 3. source ~/.bash_profile ``` ##### Edit environment setting (e.g. alias) ```bash 1. joe ~/.bash_profile 2. alias pd="pwd" //no more need to type that 'w'! 3. source ~/.bash_profile ``` ##### List environment variables (e.g. PATH) ```bash $echo $PATH # list of directories separated by a colon ``` ##### List all environment variables for current user ```bash $env ``` ##### Unset environment variable (e.g. unset variable 'MYVAR') ```bash unset MYVAR ``` ##### Show partition format ```bash lsblk ``` ##### Soft link program to bin ```bash ln -s /path/to/program /home/usr/bin # must be the whole path to the program ``` ##### Show hexadecimal view of data ```bash hexdump -C filename.class ``` ##### Jump to different node ```bash rsh node_name ``` ##### Check port (active internet connection) ```bash netstat -tulpn ``` ##### Find which link to a file ```bash readlink filename ``` ##### Check where a command link to (e.g. python) ```bash which python ``` ##### List total size of a directory ```bash du -hs . ``` or ```bash du -sb ``` ##### Copy directory with permission setting ```bash cp -rp /path/to/directory ``` ##### Store current directory ```bash pushd . $popd ;dirs -l ``` ##### Show disk usage ```bash df -h ``` or ```bash du -h ``` or ```bash du -sk /var/log/* |sort -rn |head -10 ``` ##### Show current runlevel ```bash runlevel ``` ##### Switch runlevel ```bash init 3 ``` or ```bash telinit 3 ``` ##### Permanently modify runlevel ```bash 1. edit /etc/init/rc-sysinit.conf 2. env DEFAULT_RUNLEVEL=2 ``` ##### Become root ```bash su ``` ##### Become somebody ```bash su somebody ``` ##### Report user quotes on device ```bash requota -auvs ``` ##### Get entries in a number of important databases ```bash getent database_name ``` (e.g. the 'passwd' database) ```bash getent passwd # list all user account (all local and LDAP) # (e.g. fetch list of grop accounts) ``` ```bash getent group # store in database 'group' ``` ##### Change owner of file ```bash chown user_name filename chown -R user_name /path/to/directory/ # chown user:group filename ``` ##### List current mount detail ```bash df ``` ##### List current usernames and user-numbers ```bash cat /etc/passwd ``` ##### Get all username ```bash getent passwd| awk '{FS="[:]"; print $1}' ``` ##### Show all users ```bash compgen -u ``` ##### Show all groups ```bash compgen -g ``` ##### Show group of user ```bash group username ``` ##### Show uid, gid, group of user ```bash id username ``` ##### Check if it's root ```bash if [$(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 ```bash more /proc/cpuinfo ``` or ```bash lscpu ``` ##### Set quota for user (e.g. disk soft limit: 120586240; hard limit: 125829120) ```bash setquota username 120586240 125829120 0 0 /home ``` ##### Show quota for user ```bash quota -v username ``` ##### Fork bomb # dont try this at home ```bash :(){:|:&};: ``` ##### Check user login ```bash lastlog ``` ##### Edit path for all users ```bash joe /etc/environment # edit this file ``` ##### Show running processes ```bash ps aux ``` ##### Find maximum number of processes ```bash cat /proc/sys/kernal/pid_max ``` ##### Show and set user limit ```bash ulimit -u ``` ##### Which ports are listening for TCP connections from the network ```bash nmap -sT -O localhost #notice that some commpanies might not like you using nmap ``` ##### Print out number of cores/ processors ```bash nproc --all ``` ##### Check status of each core 1. top 2. press '1' ##### Show jobs and PID ```bash jobs -l ``` ##### List all running services ```bash service --status-all ``` ##### Schedule shutdown server ```bash shutdown -r +5 "Server will restart in 5 minutes. Please save your work." ``` ##### Cancel scheduled shutdown ```bash shutdown -c ``` ##### Boardcast to all users ```bash wall -n hihi ``` ##### Kill all process of a user ```bash pkill -U user_name ``` ##### Kill all process of a program ```bash kill -9 $(ps aux | grep 'program_name' | awk '{print $2}') ``` ##### Set gedit preference on server -->you might have to install the following: apt-get install libglib2.0-bin; yum install dconf dconf-editor; yum install dbus dbus-x11; -->Check list ```bash gsettings list-recursively ``` -->Change setting e.g. ```bash gsettings set org.gnome.gedit.preferences.editor highlight-current-line true gsettings set org.gnome.gedit.preferences.editor scheme 'cobalt' gsettings set org.gnome.gedit.preferences.editor use-default-font false gsettings set org.gnome.gedit.preferences.editor editor-font 'Cantarell Regular 12' ``` ##### Add user to a group (e.g add user 'nice' to the group 'docker', so that he can run docker without sudo) ```bash sudo gpasswd -a nice docker ``` ##### pip install python package without root ```bash 1. pip install --user package_name 2. You might need to export ~/.local/bin/ to PATH: export PATH=$PATH:~/.local/bin/ ``` ##### Removing old linux kernels (when /boot almost full...) ```bash 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 ```bash sudo hostname your-new-name ``` if not working, do also: ```bash hostnamectl set-hostname your-new-hostname ``` then run: hostnamectl check /etc/hostname if still not working..., edit: /etc/sysconfig/network /etc/sysconfig/network-scripts/ifcfg-ensxxx add HOSTNAME="your-new-hostname" ##### List installed packages ```bash apt list --installed ``` or Red Hat: ```bash yum list installed ``` ##### Check which file make the device busy on umount ```bash lsof /mnt/dir ``` ##### When sound not working ```bash killall pulseaudio ``` then press Alt-F2 and type in pulseaudio ##### When sound not working ```bash killall pulseaudio ``` ##### List information about SCSI devices ```bash lsscsi ``` ##### Tutorial for setting up your own DNS server http://onceuponmine.blogspot.tw/2017/08/set-up-your-own-dns-server.html ##### Tutorial for creating a simple daemon http://onceuponmine.blogspot.tw/2017/07/create-your-first-simple-daemon.html ##### Tutorial for using your gmail to send email http://onceuponmine.blogspot.tw/2017/10/setting-up-msmtprc-and-use-your-gmail.html ##### 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) ```bash telnet 192.168.2.106 53 ``` ##### change network maximum transmission unit (mtu) (e.g. change to 9000) ```bash ifconfig eth0 mtu 9000 ``` ##### get pid of a running process (e.g python) ```bash pidof python ``` or ```bash ps aux|grep python ``` ##### ntp start ntp: ```bash ntpd ``` check ntp: ```bash ntpq -p ``` ##### remove unnecessary files to clean your server ```bash sudo apt-get autoremove sudo apt-get clean sudo rm -rf ~/.cache/thumbnails/* ``` Remove old kernal: ```bash sudo dpkg --list 'linux-image*' sudo apt-get remove linux-image-OLDER_VERSION ``` ##### Increase/ resize root partition (root partition is an LVM logical volume) ```bash 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) ```bash sudo dd if=~/path/to/isofile.iso of=/dev/sdc1 oflag=direct bs=1048576 ``` ##### Locate and remove a package ```bash sudo dpkg -l | grep sudo dpkg --purge ``` ##### Create a ssh tunnel ```bash 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) ```bash #pidof pidof sublime_text #pgrep, you dont have to type the whole program name pgrep sublim #top, takes longer time top|grep sublime_text ``` ##### Some benchmarking tools for your server [aio-stress](https://openbenchmarking.org/test/pts/aio-stress) - AIO benchmark. [bandwidth](https://zsmith.co/bandwidth.html) - memory bandwidth benchmark. [bonnie++](https://www.coker.com.au/bonnie++/) - hard drive and file system performance benchmark. [dbench](https://dbench.samba.org/) - generate I/O workloads to either a filesystem or to a networked CIFS or NFS server. [dnsperf](https://www.dnsperf.com/) - authorative and recursing DNS servers. [filebench](https://github.com/filebench/filebench) - model based file system workload generator. [fio](https://linux.die.net/man/1/fio) - I/O benchmark. [fs_mark](https://github.com/josefbacik/fs_mark) - synchronous/async file creation benchmark. [httperf](https://github.com/httperf/httperf) - measure web server performance. [interbench](https://github.com/ckolivas/interbench) - linux interactivity benchmark. [ioblazer](https://labs.vmware.com/flings/ioblazer) - multi-platform storage stack micro-benchmark. [iozone](http://www.iozone.org/) - filesystem benchmark. [iperf3](https://iperf.fr/iperf-download.php) - measure TCP/UDP/SCTP performance. [kcbench](https://github.com/knurd/kcbench) - kernel compile benchmark, compiles a kernel and messures the time it takes. [lmbench](http://www.bitmover.com/lmbench/) - Suite of simple, portable benchmarks. [netperf](https://github.com/HewlettPackard/netperf) - measure network performance, test unidirectional throughput, and end-to-end latency. [netpipe](https://linux.die.net/man/1/netpipe) - network protocol independent performance evaluator. [nfsometer](http://wiki.linux-nfs.org/wiki/index.php/NFSometer) - NFS performance framework. [nuttcp](https://www.nuttcp.net/Welcome%20Page.html) - measure network performance. [phoronix-test-suite](https://www.phoronix-test-suite.com/) - comprehensive automated testing and benchmarking platform. [seeker](https://github.com/fidlej/seeker) - portable disk seek benchmark. [siege](https://github.com/JoeDog/siege) - http load tester and benchmark. [sockperf](https://github.com/Mellanox/sockperf) - network benchmarking utility over socket API. [spew](https://linux.die.net/man/1/spew) - measures I/O performance and/or generates I/O load. [stress](https://people.seas.harvard.edu/~apw/stress/) - workload generator for POSIX systems. [sysbench](https://github.com/akopytov/sysbench) - scriptable database and system performance benchmark. [tiobench](https://github.com/mkuoppal/tiobench) - threaded IO benchmark. [unixbench](https://github.com/kdlucas/byte-unixbench) - the original BYTE UNIX benchmark suite, provide a basic indicator of the performance of a Unix-like system. [wrk](https://github.com/wg/wrk) - HTTP benchmark. ##### Show a listing of last logged in users. ```bash lastb ``` ##### Show a listing of current logged in users, print information of them ```bash who ``` ##### Show who is logged on and what they are doing ```bash w ``` ##### Print the user names of users currently logged in to the current host. ```bash users ``` ##### Stop tailing a file on program terminate ```bash tail -f --pid= filename.txt # replace PID with the process ID of the program. ``` ## Hardware [[back to top](#handy-bash-oneliner-commands)] ##### Finding Out memory device detail ```bash sudo dmidecode -t memory ``` ##### Print detail of CPU hardware ```bash 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 ```bash lsscsi|grep SEAGATE|wc -l or sg_map -i -x|grep SEAGATE|wc -l ``` ##### Get UUID of a disk (e.g. sdb) ```bash blkid /dev/sdb ``` ##### Print detail of all hard disks ```bash lsblk -io KNAME,TYPE,MODEL,VENDOR,SIZE,ROTA #where ROTA means rotational device / spinning hard disks (1 if true, 0 if false) ``` ##### List information about NIC ```bash lsscsi|grep -i 'ethernet' ``` ##### Found out power status of the server ```bash ipmitool -U your_bmc_username -P your_bmc_userpassword -I lanplus -H your_bmc_ip_address power status ``` ##### Found out server sensor temperature ```bash ipmitool sensors |grep -i Temp ``` ## Others [[back to top](#handy-bash-oneliner-commands)] ##### Remove newline / nextline ```bash tr --delete '\n' output.txt ``` ##### Replace newline ```bash tr '\n' ' ' log & ``` or ```bash some_commands 2>log & ``` or ```bash some_commands 2>&1| tee logfile ``` or ```bash some_commands 2>&1 >>outfile #0: standard input; 1: standard output; 2: standard error ``` ##### Send mail ```bash 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") ``` ##### .xls to csv ```bash xls2csv filename ``` ##### Append to file (e.g. hihi) ```bash echo 'hihi' >>filename ``` ##### Make BEEP sound ```bash speaker-test -t sine -f 1000 -l1 ``` ##### Set beep duration ```bash (speaker-test -t sine -f 1000) & pid=$!;sleep 0.1s;kill -9 $pid ``` ##### History edit/ delete ```bash ~/.bash_history ``` or ```bash history -d [line_number] ``` ##### Get last history/record filename ```bash head !$ ``` ##### Clean screen ```bash clear ``` or ```bash Ctrl+l ``` ##### Send data to last edited file ```bash cat /directory/to/file echo 100>!$ ``` ##### Extract .xf 1.unxz filename.tar.xz 2.tar -xf filename.tar ##### Install python package ```bash pip install packagename ``` ##### Delete current bash command ```bash Ctrl+U ``` or ```bash Ctrl+C ``` or ```bash Alt+Shift+# # to make it to history ``` ##### Add something to history (e.g. "addmetohistory") ```bash #addmetodistory #just add a "#" before~~ ``` ##### Sleep awhile or wait for a moment or schedule a job ```bash sleep 5;echo hi ``` ##### Backup with rsync ```bash 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! ```bash 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) ```bash cd tmp/ && tar xvf ~/a.tar ``` ##### Run command only if another command returns non-zero exit status (not finish) ```bash cd tmp/a/b/c ||mkdir -p tmp/a/b/c ``` ##### Extract to a path ```bash tar xvf -C /path/to/directory filename.gz ``` ##### Use backslash "\" to break long command ```bash cd tmp/a/b/c \ > || \ >mkdir -p tmp/a/b/c ``` ##### Get pwd ```bash VAR=$PWD; cd ~; tar xvf -C $VAR file.tar # PWD need to be capital letter ``` ##### List file type of file (e.g. /tmp/) ```bash file /tmp/ # tmp/: directory ``` ##### Bash script ```bash #!/bin/bash file=${1#*.} # remove string before a "." ``` ```bash file=${1%.*} # remove string after a "." ``` ##### Search from history ```bash Ctrl+r ``` ##### Python simple HTTP Server ```bash python -m SimpleHTTPServer ``` ##### Read user input ```bash read input echo $input ``` ##### Generate sequence 1-10 ```bash seq 10 ``` ##### Find average of input list/file ```bash i=`wc -l filename|cut -d ' ' -f1`; cat filename| echo "scale=2;(`paste -sd+`)/"$i|bc ``` ##### Generate all combination (e.g. 1,2) ```bash echo {1,2}{1,2} # 1 1, 1 2, 2 1, 2 2 ``` ##### Generate all combination (e.g. A,T,C,G) ```bash 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 ```bash foo=$( $(basename filename.gz .gz).unpacked ``` ##### Add file extension to all file(e.g add .txt) ```bash rename s/$/.txt/ * # You can use rename -n s/$/.txt/ * to check the result first, it will only print sth like this: # rename(a, a.txt) # rename(b, b.txt) # rename(c, c.txt) ``` ##### Use the squeeze repeat option (e.g. /t/t --> /t) ```bash tr -s "/t" < filename ``` ##### Do not print nextline with echo ```bash echo -e 'text here \c' ``` ##### Use the last argument ```bash !$ ``` ##### Check last exit code ```bash echo $? ``` ##### View first 50 characters of file ```bash head -c 50 file ``` ##### Group/combine rows into one row ```bash #e.g. #AAAA #BBBB #CCCC #DDDD cat filename|paste - - --> AAAABBBB CCCCDDDD cat filename|paste - - - - --> AAAABBBBCCCCDDDD ``` ##### Fastq to fasta ```bash cat file.fastq | paste - - - - | sed 's/^@/>/g'| cut -f1-2 | tr '\t' '\n' >file.fa ``` ##### Cut and get last column ```bash cat file|rev | cut -d/ -f1 | rev ``` ##### Add one to variable/increment/ i++ a numeric variable (e.g. $var) ```bash ((var++)) or var=$((var+1)) ``` ##### Some handy environment variables $0 :name of shell or shell script. $1, $2, $3, ... :positional parameters. $# :number of positional parameters. $? :most recent foreground pipeline exit status. $- :current options set for the shell. $$ :pid of the current shell (not subshell). $! :is the PID of the most recent background command. ##### Clear the contents of a file (e.g. filename) ```bash >filename ``` ##### Unzip tar.bz2 file (e.g. file.tar.bz2) ```bash tar xvfj file.tar.bz2 ``` ##### Unzip tar.xz file (e.g. file.tar.xz) ```bash unxz file.tar.xz tar xopf file.tar ``` ##### Output a y/n repeatedly until killed 'y': ```bash yes ``` or 'n': ```bash yes n ``` or 'anything': ```bash yes anything ``` For example: ```bash yes | rm -r large_directory ``` ##### Create dummy file of certain size instantly (e.g. 200mb) ```bash 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 ```bash 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) ```bash watch -n 1 wc -l filename ``` ##### Print commands and their arguments when execute (e.g. echo `expr 10 + 20 `) ```bash set -x; echo `expr 10 + 20 ` ``` ##### Print some meaningful sentences to you (install fortune first) ```bash fortune ``` ##### Colorful (and useful) version of top (install htop first) ```bash htop ``` ##### Press any key to continue ```bash 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: ```bash q -d "," "select c3,c4,c5 from /path/to/file.txt where c3='foo' and c5='boo'" ``` ##### Sreen and tmux create session and attach: ```bash screen or tmux ``` create detached session foo: ```bash screen -S foo -d -m or tmux new -s foo -d ``` detached session foo: ```bash screen: ^a^d or tmux: ^bd ``` list sessions: ```bash screen -ls or tmux ls ``` attach: ```bash screen -r or tmux attach ``` attach to session foo: ```bash screen -r foo or tmux attach -t foo ``` kill session foo: ```bash screen -r foo -X quit or tmux kill-session -t foo ``` scroll: (screeen) 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. (tmux) Ctrl-b then \[ then you can use your normal navigation keys to scroll around. Press q to quit scroll mode. Send command to all panes in tmux: ```bash Ctrl-B :setw synchronize-panes # 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 ``` ##### Cut the last column ```bash cat filename|rev|cut -f1|rev ``` ##### pass password to ssh ```bash sshpass -p mypassword ssh root@10.102.14.88 "df -h" ``` ##### wait for a pid (job) to complete ```bash wait %1 or wait $PID wait ${!} #wait ${!} to wait till the last background process ($! is the PID of the last background process) ``` ##### pdf to txt ```bash sudo apt-get install poppler-utils pdftotext example.pdf example.txt ``` ##### list only directory ```bash ls -ld -- */ ``` ##### Capture/record/save terminal output (capture everything you type and output) ```bash 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. ```bash tree #go to the directory you want to list, and type tree (sudo apt-get install tree) #output: #one/ #└── two # ├── 1 # ├── 2 # ├── 3 # ├── 4 # └── 5 # ``` ##### set up virtualenv(sandbox) for python ```bash #1. install virtualenv. sudo apt-get install virtualenv #2. Creat 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 ```bash #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 ```bash history -w vi ~/.bash_history history -r ``` ##### Decimal to Binary (e.g get binary of 5) ```bash 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) ```bash echo "00110010101110001101" | fold -w4 #0011 #0010 #1011 #1000 #1101 ``` ##### Sort a file by column and keep the original order ```bash sort -k3,3 -s ``` ##### Right align a column (right align the 2nd column) ```bash cat file.txt|rev|column -t|rev ``` ##### To both view and store the output ```bash echo 'hihihihi' | tee outputfile.txt # use '-a' with tee to append to file. ``` ##### Show non-printing (Ctrl) characters with cat ```bash cat -v filenme ``` ##### Convert tab to space ```bash expand filenme ``` ##### Convert space to tab ```bash unexpand filenme ``` ##### Display file in octal ( you can also use od to display hexadecimal, decimal, etc) ```bash od filenme ``` =-=-=-=-=-A lot more coming!! =-=-=-=-=-=-=-=-=-=waitwait-=-=-=-=-=-=-=-=-=-