Repo

InitRepo

git init main
git add .
git commit -m 'some commits'

CloneRepo

git clone someRepo

Config

Set the user info for code submission

git config --global user.name "yourname"
git config --global user.email "[email protected]"

GitHub

git remote add reponame ssh-url

# Generate ssh key
ssh-keygen -t rsa -C "[email protected]"
cat ../.ssh/id_rsa.pub

# Copy-paste the public key to Github SSH setting

# setup the upstream fro push
git push --set-upstream reponame master 

*Restore git * You need to do two commands, the first will "unstage" the file (removes it from the list of files that are ready to be committed). Then, you undo the delete.

If you read the output of the git status command (after the using git rm), it actually tells you how to undo the changes (do a git status after each step to see this).
Unstage the file:

	git reset HEAD <filename>

Restore it (undo the delete):

	git checkout -- <filename>

Shell

Variable

Define: num=1 (no space is allowed)
Apply: $num, num=2, num=$[ a+b ], let "num++"

${n} use the parameter in the script
$* and $@ shows all the parameters
$# # of parameters

Array

Define: array=(A B "C" D)
Apply: ${array[n]}, array[*/@], array[n]=2, 

关联数组（hash map） declare -A site = ([key1]=value1 [key2]=value2)

${!site[*]} return all keys
${#site[*]} return # of pairs

Operator

`expr 2 + 2`  vs  $[2+2]
[ $a -? $b ]
Comparsion: -eq -nq -gt -lt -ge -le
bool: -o -a 
logic: || &&
    echo " [ expr1 -o expr2 ] = [[ expr1 || expr2 ]]"
    echo " [ expr1 -a expr2 ] = [[ expr1 && expr2 ]]"
character: -z -n = !=
file: [ -? $file ]-r -w -x -d -f -s -e

echo

echo -e
echo -c
echo ''  不进行转义
echo `date`

printf

printf "%2s %-5c %8d %4.2f"  "-" force to the left
"" and '' are the same

test

test arguments = [ arguments ]

flow control

case
1)
;;
*)
;;
esac

function

functionname(){
    action
    [return ]
}

${n} access inputs

$? get the latest return value

***Docker in VScode ***

Install the extension
Attach Docker to the Vscode