Commonly used Linux commands

which ?? where ?? has been installed; show the full path of shell commands
pwd where am I
ls -a or -l -a all, including .file ; -l more details
ls *.txt list all(*) .txt file
cd - Back to the previous folder
cd .. Go up one upper directory layer
!cd the last command with cd; ! can be used with the other commands
cd ~ Go to $home director
history check commands that I have used

Create, copy, move, rename folders

mkdir create a directory
cp * . copy somthing to . (one dot means here-this folder; 2 dots mean the upper layer)
rm sth remove something
mv ../a ./b rename or move ../a to ./b (file/folder, including path)
mv a b rename a to be b

Preview, awk, wraggle file contents

cat myfile.txt show the file content
cat myfile.txt | less print less or more print more

check the last/first few lines
tail myfile.txt
head myfile.txt
tail -n 4 myfile.txt show the last four lines

wc -l myfile.txt check how many lines are there

cat myfile.txt| cut -c 2-9 see the specific digits
cat myfile.txt| awk '{if ($1>10), print $line}' print $line if satisfy the condition

cat myfile.txt| awk '{split($1,a,"/") split ($2,b,"/"); printf "%f %f \n%f %f", a[1], a[2], b[1], b[2]}' split by given symbols and print

cat myfile.txt| sort -nk 5 -r sort by the 5th column (-r: reverse); -n (list according to numerical order); -k field (which column)

Print, printf

print $1" "$2
printf '%s %d %.2f', string_test,$2,$3 print with formats
echo "my_notes" > note.txt write "my_notes" in a new file note.txt
echo "do not cover the existed content in olde file" >> note.txt by two ">>"

editing files: vi, vim

vi myfile.txt vi or vim to enter the vi mode
Use the following commands to play with the file

edit, save, and leave

i start to edit, insert words, editing mode
:wq! save and leave =:x
:q! leave without save
Esc leave editing mode
dd delet the whole line
yy copy the whole line
p paste
u recover the previous step

http://teacher.gtes.tp.edu.tw/~t0093/vi.htm

find the keywords

/keword
n show next keyword

go to specific line

The last line G
The #n line 1gg 157gg
The #n column in given line n|

replace the given words by

:%s/pattern/replacement Replace the first occurrence of "pattern" with "replacement" on all lines
:[range]s/{pattern}/{string}/[flags] [count] The command looks for a "{pattern}" on each line in [range] and replaces it with a {string}. The instruction is multiplied by a positive integer called [count]

print time

date system time variable

now=$(date +"%T")  
echo "Current time : $now"

Search for specific string in files or files in directory

grep keywords * find keywords in all files in this folder
grep -c "linux" long.txt count (-c) the number of times the pattern repeats

sed SCRIPT INPUTFILE...
sed -i 's/to_be_replaced/replace/' /path/file.txt replace string by new string in file.txt

find [flags] [path] -name [expression] searches for files in a directory hierarchy based on a regex expression

Commands without pop up message or being interrupted

nohup commands & running at the background and would not be interrupted

Monitoring activities

top check all operating procedures
htop check machine’s resources
ps check the processes your current shell session is running
kill PID kill project ID
killall -u myname kill all procedures started by -u username

change authority for files or folders

chmod +x file.txt make the file exacutable
chmod 700 myfolder only myslef can rwx, other has no authority for all
r (read=4) w (write=2) x (execute=1) -(nono=0)
owner, ther group member, the others

https://ftp.kh.edu.tw/Linux/Redhat/en_6.2/doc/gsg/s1-navigating-chmodnum.htm
https://www.cs.nccu.edu.tw/~lien/UNIX/Command/chmod.htm

ssh

ssh -X, -Y
sshpass -p <my_password> ssh <username>@<hostname>
sshpass -p <my_password> scp <username>@<hostname>:folder/file .
ssh -t XXX001@140.112.XX.XX ssh -t yyyy@140.112.y.yy go to y station through x station

Download files

from remote station

up/download single file

scp ./abc.dat wanlin001@xxx.xxx.xxx:/home/wanlin001/working_folder
scp wanlin001@xxx.xxx.xxx:/home/wanlin001/working_folder ./abc.dat

then, enter password

up/download folder
add -r scp -r

rsync synchronize data on disk with memory
rsync -P -r
rsync -n source where_to_store -n skip repeated files

-P, –progress，show progress
-a, –archive
-v, –verbose
-z, –compres
-u, –update

from a link

wget url
git clone from github

uncompress files

tar
Unzip various file formats

tar xvf FileName.tar
gzip -d FileName.gz 
gunzip FileName.gz
tar zxvf FileName.tar.gz
bunzip2 FileName.bz
tar jxvf FileName.tar.bz
bzip2 -d FileName.bz2
bunzip2 FileName.bz2
tar jxvf FileName.tar.bz2
tar Jxvf FileName.tar.xz
tar Zxvf FileName.tar.Z
tar zxvf FileName.tgz
tar zxvf FileName.tar.tgz
unzip FileName.zip
rar e FileName.rar
tar -I zstd -xvf FileName.tar.zst

x-> uncompress
c-> compress

https://note.drx.tw/2008/04/command.html

Check hardware

lsblk list unpartitioned and unmounted disks
free -m RAM size
lscpu check cpu
df check hard disk storage
df -h show for human
df -m show by MB
du /folder/ check given folder
du -s -h /path_to/folder/ -s summary of this folder
du -h ./folder/ | sort -rn -rn (reverse), rank according to the size of files in this folder
du -h folder -d 1 show how many layers of directories: -d or --max-depth=
grep 'core id' /proc/cpuinfo |wc -l check number of cpu

tree show the directory tree structure, sudo apt install tree
tree /path/to/directory

Commands used by superusers

Users

add users
sudo useradd
sudo paaword
sudo useradd -f 45 newusr only 45 days for this newusr
sudo userdel --remove newusr delet the user and its home directory
sudo usermod -aG sudo newuser assign newuser as a superuser
su - newuser switch user
passwd change password
last username login history

Disk

https://judysocute.com/blog/linux-硬碟掛載/

sudo umount -f -f force
mount mount
reformat
RAID mdadm
ln -s ../foler/store ./link create a soft link: the "link" will point to "store"

Netfilter

IPtable

git

git status
git add .
git commit -m "my comments"
git log
git show XDNFLOOGEGML(commit series)
git reset --hard XXXXX