Modified: July 19 2024

Link to video.

The Basics of Shell

Shell, terminal, console, command line, all are essentially the same thing.

Commands

  • ls: lists out all items in the current (target) directory
    • You can pass some flags to change the output
    • -latrh will produce long list format, all files, sorted by time, in reverse, with human readable file sizes
    • You can also use a path as an argument, as well as a combination of both flags and path
  • cd: change directory
  • pwd: shows path to current work directory
  • echo: lets you print some text
  • cat: lets you print the content of a file
  • touch: creates a file if it doesn’t exist; changes the timestamp if it does
  • cp: lets you copy a file or directory to a target destination
  • move: like copy, but moves it instead
  • rm: removes a file or directory
    • Need to use -r to delete a directory
    • You can add f to forcefully delete it
  • ln: creates a symlink in a file to another location
    • Similar to a reference object in programming
  • less: lets you view text content in a scrollable format
    • Often more useful than cat, since you can search easily
  • more: less than less, but more on the screen and can only go forward
  • man: shows the manual for the command you need
    • Similar to using --help after a command
    • One documentation I’d love to go through is note taking manual pages for all these commands.
  • grep: lets you pattern match against text content
    • You can install ripgrep which is like grep, but faster
  • find: finds a file or directory
    • Syntax can be weird, so might be better to install fd, a faster easier find
  • sed: a stream editor, allowing you to make changes to an incoming stream of text
    • Usually useful to find and replace text
  • awk: allows for programming logic
    • Useful for one-liners, grabbing specific things from a file
  • sort: sorts text content
  • head: lets you see the first few lines of a file
  • tail: lets you see the last few lines of a file

The pipe operator, |, allows you to chain commands into one another. The standard output from your first command will be fed into your second command, so on so forth.

  • xargs: takes the contents of whatever you pipe into it and splits it into different chunks
    • For each chunk, it will pass it as an argument into whatever command specified

Subshell, or $(command), injects the output of whatever command/pipeline you defined, placing it wherever you defined the subshell.

You can use the > command, or redirection operator, sends the standard output of the source file into whatever file you choose. Two greater than signs will append, not overwrite, or creates it if it doesn’t exist.

  • fzf: a fuzzy finder. Run it by itself and you can easily search for items.
  • compgen: combine with -c to see all commands

Fun Commands

Let’s say we take the following command: compgen -c | fzf | xargs man. This will produce all available commands in a fuzzy finder, then anyone we choose will produce it’s manual.

We can take this a step further. If we use alias, a method of generating our own commands, and call it something like fman, we can write the following statement to produce a new command:

alias fman = 'compgen -c | fzf | xargs man'

Running fman from now on will execute the pipeline we described earlier. To make it easier, we can always make sure it’s there by adding the above code to your bash.bashrc file, by adding the line at the end of the file.

In order to find the largest file in a directory, we can use:

du -ah . | sort -hr | head -n 10

Here, we are using du to get file sizes, with the -ah for aggregate view with human readable text. That is fed into a sort in reverse order, and finally, head to view with just 10 lines at a time.

Some helpful hotkeys:

  • ctrl+c: kill active process
  • ctrl+k: exit shell
  • ctrl+l: clear screen
  • ctrl+z: put process in background
  • ctrl+a: go to the front of the line
  • ctrl+e: go to the end of the line
  • ctrl+b: go back one character
  • ctrl+f: go forward one character
  • alt+f: go forward one word
  • alt+b: go back one word
  • !!: run previous command (also known as bang bang)
  • !<cmd>: run previous matching command
  • ctr+x ctrl+e: open line in $EDITOR

Big Tips for Success

  1. Use the man pages (or tldr)
  2. Use the pipelines and subshells for a good time
  3. Use alias and scripts to save your work
  4. Use fzf