#+title: Lesson 05 | Command line Environment
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* Links
#+attr_html: :class links
- [[../toc.org][TOC | Missing Semester]]
- [[https://www.youtube.com/playlist?list=PLyzOVJj3bHQuloKGG59rS43e29ro7I57J][Playlist: Missing Semester]]
- [[https://www.youtube.com/redirect?event=video_description&redir_token=QUFFLUhqbVVJc2RzZ25nMmlrVW5zVGRsTS1fX2ladmRPQXxBQ3Jtc0ttWjQ5Ujcyd19TekNncTZGNEp1eDc3RWhzTzhvMW9oSTFoUl9JbGt1Mi0yU3FLc00wVUx1UXNJdFQxTjBjMWphdUZxNnU1WUYzTmFqd3RRemNLUDBJMlZkV3B0SnB4RVhpaUhvWWtnc1RISW1WVzdYWQ&q=https%3A%2F%2Fmissing.csail.mit.edu%2F2020%2Fcommand-line%2F&v=e8BO_dYxk5c][class notes]]

- Curr: https://youtu.be/e8BO_dYxk5c?si=7tmshQsaihcvs-aP&t=2018

*** timestamps
:PROPERTIES:
:CUSTOM_ID: timestamp
:END:

#+attr_html: :class playlist
+ [[https://youtu.be/e8BO_dYxk5c?si=A-imhHunQCtp_-Oz][00:00 - introduction]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=138s][02:18 - Job Control]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=227s][03:47 - Signal Interrupts]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=360s][06:00 - Python Program]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=672s][11:12 - The Kill Command]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=881s][14:41 - Terminal Multiplexer]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=1112s][18:32 - The Key Bindings]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=1536s][25:00 - Dot Files]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=1799s][29:59 - Context Based Configuration File]] *current*
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=2004s][33:24 - Terminal Emulator]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=2196s][36:36 - Aliases]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=2286s][38:06 - Common Folder Structure]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=2344s][39:04 - Symlinks]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=2552s][42:32 - ssh]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=2715s][45:15 - ssh keys]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=3057s][50:57 - ssh config]]
+ [[https://www.youtube.com/watch?v=e8BO_dYxk5c&t=3231s][53:51 - changing the prefix]]

* notes

** topics
- job control
- terminal multiplexers
- dot files / how to configure
- work with remote machines

** job control
*** sleep
- puts process to sleep for a specified amount of time
- exit by typing Ctrl-C

*** Ctrl-C
- sends SIGINT - signal interrupt
- man signal will show the list of signals

** signals
- SIGQUIT :: signal sent when we want to quit
- SIGTERM :: similar to quit but not in term
- SIGHUP :: when we have processes running but still want to close

*** pausing
- SIGSTOP :: pause execution of program
- SIGCONT :: continue program

*** python library
- use import signal

#+BEGIN_SRC python
import signal
def handler(signum, frame):
    printf("signal received")

signal.signal(signal.SIGINT, handler)
#+END_SRC

- the above would catch a Ctrl-C and run it through handler
- you use this by catching a Ctrl-C and running any saves or cleanup before exiting

** nohup and jobs
- allows for a process to continue livign when the terminal is killed

*** example
- sleep put the process to sleep
- '&' puts the process in the background
  - wont take over the process

#+BEGIN_SRC bash
nohup sleep 2000 & python somprog.py
#+END_SRC

*** jobs
- ~jobs~
will show the suspended and running processes in background

- how to restart a suspended process
  - type 'jobs' to see what there is in this terminal
  - the find the jobs number, ie [1] or [2]
  - use the 'bg' command
    #+BEGIN_SRC bash
    bg %1
    #+END_src


** kill command
- allows you to send any kind of signal to a job

- e.g. "stop" will suspend but not close the job

*** some commands
- HUP :: Hang Up
- STOP :: suspend
- KILL :: kill it no matter what


** Terminal Multiplexer
*** overview
- tmux
- lets you create workspaces that you can work in
- rearrange the environment
- have different settings

*** core concepts
- hierarchy
  - sessions
  - windows
  - panes


** dot files
*** alias
- remap a source series of characters to a longer series
- alias takes a single argument, ie, do not use spaces
- to show what an alias refers to pass the alias to the alias command
  - e.g.
#+begin_src bash
~/somedirectory >>> alias myaliasedcommand
myaliasedcommand='ls -lah'
#+end_src

**** examples
- make an alias "ll" for a list command with flags
#+begin_src bash
alias ll="ls -lah"
#+end_src

- make an alias for git status
#+begin_src bash
alias gs="git status"
#+end_src

- alias to prompt for an override
#+begin_src bash
alias mv="mv -i"
#+end_src

*** text based configuration 'dot files'
- called 'dot files' because they start with a dot
  - .bashrc
    - must be in the home directory
  - PS1
    - prompt variable for your prompt
    - you can set it in the .bashrc file
    - ~PS1=" >> "~

  - .vimrc
    - vim configuration file

**  terminal emulator