https://github.com/hchiam/learning-bash-scripts

Learning Bash Scripts
https://github.com/hchiam/learning-bash-scripts

bash shell

Last synced: over 1 year ago
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Learning Bash Scripts

Host: GitHub
URL: https://github.com/hchiam/learning-bash-scripts
Owner: hchiam
License: mit
Created: 2019-10-10T17:58:16.000Z (over 6 years ago)
Default Branch: main
Last Pushed: 2025-02-03T05:22:26.000Z (over 1 year ago)
Last Synced: 2025-03-19T08:03:41.879Z (over 1 year ago)
Topics: bash, shell
Language: Shell
Size: 150 KB
Stars: 1
Watchers: 2
Forks: 0
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE

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# Learning Bash Scripts

Just one of the things I'm learning.

[You type commands in a terminal or console, and those commands get translated by the shell for the kernel to perform.](https://www.quora.com/What-is-the-difference-among-shell-console-terminal-and-kernel-Also-what-is-the-difference-between-shell-and-application-programs)

A nice article on key things to know: https://www.joshwcomeau.com/javascript/terminal-for-js-devs (my own summary notes are below)

To enable running a script upon click, you need to edit permissions. For example, for `chrome-incognito-shortcut.app`:

```bash
chmod 744 chrome-incognito-shortcut.app
```

## Related Repos

## `>` and `<` and `>>` and `<<` in bash

https://superuser.com/questions/480599/with-regards-to-piping-commands-what-are-the-greater-than-and-less-than

- `>` = redirect output = "(over)write to", e.g.: `echo 'hello' > file.txt`
- `<` = redirect input = "read", e.g.: `cat < file.txt` (same as just `cat file.txt`)
- `>>` = append to end of file, e.g.: `echo 'new last line of text' >> file.txt`
- `cat << EOF >> file.txt` = "start multiline input session that ends when you type `EOF` and hit Enter" (but personally, `nano` seems to do this simpler)

## Useful `git` commands

- `git commit --amend`

- `git reset HEAD~1` to "un-commit"

- `git pull origin dev` (if you want to merge commits into `dev` branch into your local branch) and then type `:qa` and hit enter. Now you can `git push`.

- `git tag ; git push --tags` (and then you can draft a new release on the same tag name to add details to it on GitHub)

From :

- `git update-index --skip-worktree your-file-to-ignore-future-revisions-for.txt`
- `git update-index --no-skip-worktree your-file-to-start-watching-revisions-for.txt`

From :

- `git status -sb`
- git hooks
- Try using git `bisect` with "binary search" automation to find the breaking change

```bash
git bisect start
git bisect good c5ba734 # if c5ba734 is a commit without the bug
git bisect bad 6c093f4 #if 6c093f4 is a commit with the bug
# run test: git bisect run ./test-bug (or: git bisect run jest)
git bisect bad # if the current commit has the bug
git bisect good # if current commit does not have the bug
# (repeats until find the first commit with the bug)
git bisect reset # or: git bisect reset HEAD (or: git bisect reset )
```

```bash
git rebase -i --exec "yarn test" d294ae9 # test all commits from d294ae9 to HEAD, until hit first failing commit
```

From :

- `git rm --cached ` to stop tracking `` in version control
- `git diff --staged`
- `git diff branch1..branch2`
- `git commit --amend` to add more changes to the last commit
- `git cherry-pick ` to bring in a commit from a different branch
- `git checkout ` to bring in a file from a differnt branch

- `git reset `
- `git reset --hard HEAD~1` = undo last commit and rewrite history (then `git push -f` to push rewritten history)
- `git reset --hard HEAD~n # where n is the last n commits` = undo last n commit and rewrite history (then `git push -f` to push rewritten history)
- `git reset --hard ` = undo comments and rewrite history (then `git push -f` to push rewritten history)
- `--soft` = uncommit but still staged; `--mixed` = uncommit+unstage, but changes kept locally; `--hard` = uncommit+unstage+delete changes

- `git stash` to save your changes to top of stash stack (add `-u` to stash untracked files as well)
- `git stash list` to see what's in your stash
- `git stash save "message to go along with changes"`
- `git stash pop`

From :

- `git stash save nameforlater`

- and then later `git stash list` (note the index)
- and then `git stash apply ` to use ``

- `git branch -M main` to rename branch to main, and then `git push -u origin main` ([more info](https://www.git-tower.com/learn/git/faq/git-rename-master-to-main/))

- `git log --graph --oneline --decorate` for a pared-down git log

- lots more git tips at a [Fireship.io YouTube video](https://www.youtube.com/watch?v=ecK3EnyGD8o)

### How to revert changes of a git push:

This shows the commit hash: (looks like `l0ngStr1ng0fL3t7er5AndNum83rz`)

```bash
git log
```

then use the hash of the commit you want to revert: (and when you're in the in-CLI editor, type `:qa` and then hit Enter)

```bash
git revert l0ngStr1ng0fL3t7er5AndNum83rz
```

### How to create a branch with no history

https://stackoverflow.com/a/34954852

```bash
git checkout --orphan
git commit
git push
```

## Random Notes

Get file info like edit date: `stat filename`

Example of script used by Travis CI `npm run build` to copy files to `/public` folder: [copy-to-public-folder.sh](https://github.com/hchiam/hchiam.github.io/blob/master/copy-to-public-folder.sh)

Example of script used to generate and insert a package SemVer number for a JS file: [package.sh](https://github.com/hchiam/_2DNote/blob/master/package.sh)

Exit/quit:

```bash
exit
```

### Get list of globally installed packages

`yarn global list`

`npm list -g --depth 0` for just top-level

`npm list -g browser-sync` or a specific package (this example checks if `browser-sync` is installed globally)

### npm scripts that accept parameters

Examples I set up in package.json:

```json
{
"test": "tsc $npm_config_name.ts --lib es6,dom && node $npm_config_name.js",
"demo": "echo \"HELLO $npm_config_file_name.ts GOODBYE (\\$npm_config_whatever will match --whatever=...)\""
}
```

So you can do this:

```bash
npm run demo --file_name=someFileName
# prints out: HELLO someFileName.ts GOODBYE [...]
```

and:

```bash
npm run test --name=sameFileName
# will run: tsc sameFileName.ts --lib es6,dom && node sameFileName.js
```

### Install package without dynamic version (i.e. without caret ^)

```sh
npm install --save-exact
```

so you get `1.2.3` instead of `^1.2.3` in your `package.json`

https://stackoverflow.com/questions/58638817/what-is-the-purpose-of-using-save-exact#:~:text=--save-exact%20will%20generate%20the%20next%20package.json%20code

### Actually upgrade node

You can upgrade to the latest `npm` with `npm install -g npm@latest`

But installing node manually doesn't always work, and using `n` or clean cache didn't seem to work for me.

For Mac/OSX, try this first:

```bash
brew install node
```

Otherwise this:

```bash
nvm install node --lts
node -v
```

If you accidentally installed the latest but want to downgrade to the last stable instead:

```bash
nvm install 14.15.0 # whatever the latest unstable versioni on https://nodejs.org/en/
nvm use 14.15.0
```

### switching from `bash` to `zsh`: (and back)

### Format whole directory instead of waiting for each file save in VSCode

```bash
prettier --write .
```

```bash
npx prettier --write .
```

### how to sync forked repo with the original repo

```bash
git remote add upstream https://github.com//.git
git fetch upstream
```

### `gh` CLI commands

### setting up GitHub PATs (Personal Access Tokens)

For `gh` CLI: copy your PAT, run `gh auth login`, and paste your PAT when prompted to.

For npm pkg: copy your PAT, open `~/.npmrc`, and paste your PAT to be the "TOKEN" part of a string `//npm.pkg.github.com/:_authToken=TOKEN` in that `~/.npmrc` file.

### quickly set up a basic server to serve index.html (or whatever's in the current folder)

```sh
python3 -m http.server 8000
```

or set up shortcut `srv` in .bash_profile:

```
alias srv='python3 -m http.server 8000'
```

## https://www.joshwcomeau.com/javascript/terminal-for-js-devs

- Bash ≈ Zsh
- the terminal is kinda like the console log in browser dev tools, but can switch between shell languages
- `echo` ≈ `console.log`
- `$` notation is just for start of prompt
- `pwd` = print the current working directory folder path
- `ls` = list current folder files/subfolders
- `ls -la` = `-l`ong data too like updated dates, and `-a`ll files including hidden files/folders
- `cd` = change directory
- `~` = home folder, like `/Users/yourusernamehere`
- `.` = current folder
- `..` = parent folder
- use the tab key to auto-complete!
- `rm` = remove
- `rm -r foldername` = remove `foldername` and `-r`ecursively inside it too
- `rm -rf foldername` = do that, but `-f`orce remove regardless of permissions
- `man somecommand` = show a printout of the `man`ual for somecommand
- hit `q` to `q`uit (arrow keys to scroll)
- `ping 8.8.8.8` = continuously check latency against IP address 8.8.8.8 (Google's DNS server), which can be used to continuously check if the server is online (`Ctrl`+`c` or `Ctrl`+`d` to stop)
- `-` = "previous"
- `cd -` = toggle to previous folder
- `git checkout -` = toggle to previously-checked-out branch
- `alias hi='echo "Hello world!"'`
- now you can just do `hi` to get a printout of `Hello world!`
- `command1 && command2` = do command1 and then to command2
- stuck in Vi/Vim? `Ctrl`+`c` won't work! hit `Escape` -> `:` -> `q!` -> `Enter`
- common web dev tasks: https://www.joshwcomeau.com/javascript/terminal-for-js-devs/#common-development-tasks
- reinstall dependencies: `rm -rf node_modules; npm install;`

## more to learn for unix:

- https://www.tutorialspoint.com/unix/unix-special-variables.htm
- https://www.tutorialspoint.com/unix/unix-using-arrays.htm
- https://www.tutorialspoint.com/unix/unix-basic-operators.htm
- https://www.tutorialspoint.com/unix/unix-decision-making.htm
- https://www.tutorialspoint.com/unix/unix-shell-loops.htm
- https://www.tutorialspoint.com/unix/unix-quoting-mechanisms.htm for getting variables and special characters parsed or not parsed in strings
- https://www.tutorialspoint.com/unix/unix-io-redirections.htm - there's more to it than just > file
- https://www.tutorialspoint.com/unix/unix-shell-functions.htm
- https://www.tutorialspoint.com/unix/unix-manpage-help.htm
- https://www.tutorialspoint.com/unix/unix-useful-commands.htm

## 5 linux command tricks from fireship.io

https://www.youtube.com/shorts/fwBIZRq-vzY

- `mkdir`, but with multiple sibling folders at the same time:
- `mkdir folder` then:
```sh
mkdir -p folder/{sibling1,sibling2}/{commonA,b,c}
```
- gives you this:
```txt
/folder
/sibling1
/commonA
/b
/c
/sibling2
/commonA
/b
/c
```
- `cd`, but back to where you last were instead of `cd ..` a bunch of times:
- `cd ./somewhere/deeply/nested` then to get back to `./`:
```sh
cd -
```
- `touch`, but create a bunch of files with names with a pattern:
- ```sh
touch file{1..10}.txt
```
=
```txt
file1.txt
file2.txt
file3.txt
file4.txt
file5.txt
file6.txt
file7.txt
file8.txt
file9.txt
file10.txt
```
- (note: the one-liner command doesn't pad with 0s on my machine despite `{01..10}`)
- two 0-padding alternatives that worked for me: (`%02g` = zero-padding of width 2 of general number format)
- ```sh
touch $(seq -f "file%02g.txt" 1 10)
```
- or this: (the space after `txt ` matters for this one!)
```sh
touch $(printf "file%02g.txt " {1..10})`
```
- `tail err.log` to read a file, but `tail -f err.log` to "follow" changes
- (note: doesn't seem to print out the right contents if i edit in another tab with `nano`)
- `history`, but to get the last 5 commands:
- ```sh
history 5
```

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