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Shell commands

Basic commands with examples

basics

# this is comment
ls
ls -al
touch hello.txt
touch --help
man touch
echo hello world
echo "hello world"
MY_TEXT="ABC"
echo $MY_TEXT
cat hello.txt
cp hello.txt hello2.txt
mv hello.txt hello1.txt
rm hello*.txt
mkdir abc
cd abc
cd /
cd ~
cd
cd ..
cd .
cd -
rmdir abc
clear
history
exit

redirection

echo "hello world" > hello.txt
echo "hi world" >> hello.txt
echo "hello world" > /dev/null
ls 1> out.txt 2> error.txt
ls -z 1> out.txt 2> error.txt

pipe

cat hello.txt|head

search

whereis python3
which python3
grep search_text -rniH .
find . |grep hello
find . |less

read file

less hello.txt
head hello.txt
tail hello.txt
tail -f log.txt

process and job management

ps aux
ps aux |grep python
top
htop
pstree
tail -f log.txt &
jobs
fg
bg
kill -9 12345
nohup a_long_remote_script.sh &

network

ping google.com
wget http://google.com
wget https://raw.githubusercontent.com/uiuc-cse/data-fa14/gh-pages/data/iris.csv
ifconfig
ssh example_account@example.com
scp hello.txt example_account@example.com:/home/example_account/
scp demo@test.rebex.net:/readme.txt ./

environment variables

env
FOO=BAR a_script.sh
source venv/bin/activate
. venv/bin/activate

etc

ln -s target_file link_file_to_create
nano hello.txt

Example bash script

#!/bin/bash
TALKING_TO=WORLD

echo "Hello $TALKING_TO! ($FOO, $1, $2)"

Run with a environment variable

chmod +x hello.sh
FOO=BAR ./hello.sh
  • #!/bin/bash is called a shebang line. By that the operating system decide the interpreter to run.
  • For a python script it can be like #!/usr/bin/env python3 to be more portable across different systems.

python development

python3 -m venv venv
. venv/bin/activate
pip install numpy
pip install -U pip
pip freeze
pip freeze > requirements.txt
pip install -r requirements.txt
python hello.py
deactivate
code .

(pyenv)

# install pyenv with the guide from https://realpython.com/intro-to-pyenv/

pyenv versions
pyenv install --list
pyenv install 3.8.12
pyenv global
pyenv global 3.8.12
pyenv local
pyenv local 3.8.12

# update the python version list if you don't see the latest versions
cd ~/.pyenv && git pull && cd -

git commands to get source codes

git clone git@github.com:hotohoto/ml_course.git
cd ml_course
git fetch
git log origin/master
git reset --hard origin/master

additional topics

  • soft link
    • ln -s target_file link_file_name
  • return code or error code
    • $?
    • 0: success
    • non-zero: fail
  • &&
  • ||
  • watch
    • watch ps aux
  • find and execute
  • awk
  • nano or vim
  • apt or brew
  • arguments for bash script
  • if statement
  • for statement
  • telnet to check if a port is open
  • ssh-add
  • ssl 🔑 gen for git configuration

Remarks

IO devices

  • 0: /dev/stdin
  • 1: /dev/stdout
  • 2: /dev/stderr
  • /dev/null