Content

• Header
  • functions
  • Extract
  • Compress
  • BIOS from linux
  • Find ip
  • xrdp/remote desktop
  • sed
    • replace
  • Lock screen by bash
  • RAM testing inspection
  • check my pc ip at 109 by login to hpc2021.hku.hk
  • soft link
• Gnuplot
• ssh
  • password-less login: client
  • sshfs

Header

#!/bin/bash

chmod +x filename

for var in 'abc' 'erere' 'erererss'; do
cp ${var} file
done

command 1 && command 2 go to next command only if the previous one is successful

command > log.txt 2>&1 & save log and error to log.txt file. The first > refers to the standard output redirection (to log.txt here). The second 2> refers to the error output redirection, it was redirected to the ‘log’ category by &1 (same log.txt here). The last & refers to no standard output and run in the background.

[] can be a comparison between two strings:[ "$str1" = "$str2" ]

[ -f "abc.abi" ] && echo "It is a file."
Or
if [ -f "abc.abi" ]; then
  echo "It is a file."
fi

determine whether abc.abi is a file, if true, output “It is a file.” on command line

Applications:

cp `find -name 'it_is_file_name'` folder/

Copy file with name it_is_file_name into folder/

functions

function my_func {
Shell script
}

Extract

tar -zxvf ./file.tar.gz
tar -xvjf ./file.tar.bz2
tar -xf ./file.tar

Compress

tar -zcvf name-of-archive.tar.gz ./directory

BIOS from linux

systemctl reboot --firmware-setup

Find ip

ifconfig
or 
nmcli device show

xrdp/remote desktop

• Boot

  who -u
  

• find :0, referring to the local display
• kill the pid
• Use remote desktop to login

${parameter/pattern/string} Replace ‘pattern’ in ‘parameter’ with ‘string’

tmp=${a#*_}remove prefix ending in “_”

b=${tmp%_*}remove suffix starting with “_”

sed

sed -i 's/abc/XYZ/g' /tmp/file.txt

which will invoke sed to do an in-place edit due to the -i option. The g flag use to replace globally without line number, i.e. do not substitute only the first occurrence on each input line. This can be called from Bash.

replace

sed -i '3s/origin/new/' /tmp/file.txt

replace the origin string to new in line 3

Lock screen by bash

gnome-screensaver-command -l

RAM testing inspection

sudo dmidecode --type memory | less

check my pc ip at 109 by login to hpc2021.hku.hk

last -a | grep ynl08

soft link

ln -s {source-filename} {symbolic-filename}

for example, I have a directory at /home/heliosynl/test and I want it a new name is /data/newname, I can do

ln -s /home/heliosynl/test /data/newname

it will create a softlink name newname at /data/ directory, pointing to /home/heliosynl/test

Gnuplot

gnuplot -p -e "set terminal dumb; plot '' u 1:3 w l" 

plot in terminal

• -p for new window to show
• -e for in-line command, using ; to separate lines
• plot 'filename' u 1:2 w l (using 1:2 default)
• set terminal dumb for plotting in terminal but not new window
• plot 'filename' u 1:2 w l t 'labelname'

check gnuplot cheat sheet

ssh

sudo apt install openssh openssh-server

• start ssh server: sudo service sshd start or sudo systemctl start sshd
• check server status: sudo service sshd status or sudo systemctl status sshd

password-less login: client

• Generate private and public keys
  • ssh-keygen
    • press Enter is ok
  • can find:
    • public key at ~/.ssh/id_rsa.pub
    • private key at ~/.ssh/id_rsa
  • copy public key to the server
    • ssh-copy-id name@serverip
    • instead, copy the content in id_rsa.pub to server side ~/.ssh/authorized_keys

      sshfs

• Install openssh openssh-server
  • It is okay when the machine can be connected with other machine through ssh
• Install sshfs
  • sudo apt install sshfs
• Then add the current user into the fuse group (administrative group of using sshfs)
  • Check if there is a fuse group: cat /etc/group | grep 'fuse'
  • If there is not: sudo groupadd fuse
• Then: sudo usermod -a -G fuse your_username