Bash Commands That Save Me Time and Frustration

Bash Commands

Bash Commands That Save Me Time and Frustration

Here's a list of bash commands that stand between me and insanity.

Bash Commands That Save Me Time and Frustration

Here's a list of bash commands that stand between me and insanity.

https://bryanguner.medium.com/a-list-of-all-of-my-articles-to-link-to-future-posts-1f6f88ebdf5b

bgoonz/bash-commands-walkthrough _to accompany the medium article I am writing. Contribute to bgoonz/bash-commands-walkthrough development by creating an…_github.com

I will include the code examples as both github gists (for proper syntax highlighting) and as code snippets adjacent to said gists so that they can easily be copied and pasted… or … if you're like me for instance; and like to use an extension to grab the markdown content of a page… the code will be included rather than just a link to the gist!

Here's a Cheatsheet:

Getting Started (Advanced Users Skip Section):

✔ Check the Current Directory ➡ pwd:

On the command line, it's important to know the directory we are currently working on. For that, we can use pwd command.

It shows that I'm working on my Desktop directory.

✔ Display List of Files ➡ ls:

To see the list of files and directories in the current directory use ls command in your CLI.

Shows all of my files and directories of my Desktop directory.

To show the contents of a directory pass the directory name to the ls command i.e. ls directory_name.
Some useful ls command options:-

OptionDescriptionls -alist all files including hidden file starting with '.'ls -llist with the long formatls -lalist long format including hidden files

✔ Create a Directory ➡ mkdir:

We can create a new folder using the mkdir command. To use it type mkdir folder_name.

Use `ls` command to see the directory is created or not.

I created a cli-practice directory in my working directory i.e. Desktop directory.

✔ Move Between Directories ➡ cd:

It's used to change directory or to move other directories. To use it type cd directory_name.

Can use `pwd` command to confirm your directory name.

Changed my directory to the cli-practice directory. And the rest of the tutorial I'm gonna work within this directory.

✔ Parent Directory ➡ ..:

We have seen cd command to change directory but if we want to move back or want to move to the parent directory we can use a special symbol .. after cd command, like cd ..

✔ Create Files ➡ touch:

We can create an empty file by typing touch file_name. It's going to create a new file in the current directory (the directory you are currently in) with your provided name.

I created a hello.txt file in my current working directory. Again you can use `ls` command to see the file is created or not.

Now open your hello.txt file in your text editor and write Hello Everyone! into your hello.txt file and save it.

✔ Display the Content of a File ➡ cat:

We can display the content of a file using the cat command. To use it type cat file_name.

Shows the content of my hello.txt file.

✔ Move Files & Directories ➡ mv:

To move a file and directory, we use mv command.

By typing mv file_to_move destination_directory, you can move a file to the specified directory.

By entering mv directory_to_move destination_directory, you can move all the files and directories under that directory.

Before using this command, we are going to create two more directories and another txt file in our cli-practice directory.

mkdir html css touch bye.txt

Yes, we can use multiple directories & files names one after another to create multiple directories & files in one command.Moved my bye.txt file into my css directory and then moved my css directory into my html directory.

✔ Rename Files & Directories ➡ mv:

mv command can also be used to rename a file and a directory.

You can rename a file by typing mv old_file_name new_file_name & also rename a directory by typing mv old_directory_name new_directory_name.

Renamed my hello.txt file to the hi.txt file and html directory to the folder directory.

✔ Copy Files & Directories ➡ cp:

To do this, we use the cp command.

You can copy a file by entering cp file_to_copy new_file_name.

Copied my hi.txt file content into hello.txt file. For confirmation open your hello.txt file in your text editor.

You can also copy a directory by adding the -r option, like cp -r directory_to_copy new_directory_name.

The -r option for "recursive" means that it will copy all of the files including the files inside of subfolders.

Here I copied all of the files from the folder to folder-copy.

✔ Remove Files & Directories ➡ rm:

To do this, we use the rm command.

To remove a file, you can use the command like rm file_to_remove.

Here I removed my hi.txt file.

To remove a directory, use the command like rm -r directory_to_remove.

I removed my folder-copy directory from my cli-practice directory i.e. current working directory.

✔ Clear Screen ➡ clear:

Clear command is used to clear the terminal screen.

✔ Home Directory ➡ ~:

The Home directory is represented by ~. The Home directory refers to the base directory for the user. If we want to move to the Home directory we can use cd ~ command. Or we can only use cd command.

MY COMMANDS:

1.) Recursively unzip zip files and then delete the archives when finished:

here is a folder containing the before and after… I had to change folder names slightly due to a limit on the length of file-paths in a github repo.

find . -name "*.zip" | while read filename; do unzip -o -d "`dirname "$filename"`" "$filename"; done;

find . -name "*.zip" -type f -print -delete

2.) Install node modules recursively:

npm i -g recursive-install

npm-recursive-install

3.) Clean up unnecessary files/folders in git repo:

find . -empty -type f -print -delete #Remove empty files

# -------------------------------------------------------
find . -empty -type d -print -delete #Remove empty folders

# -------------------------------------------------------

# This will remove .git folders...    .gitmodule files as well as .gitattributes and .gitignore files.

find . \( -name ".git" -o -name ".gitignore" -o -name ".gitmodules" -o -name ".gitattributes" \) -exec rm -rf -- {} +

# -------------------------------------------------------

# This will remove the filenames you see listed below that just take up space if a repo has been downloaded for use exclusively in your personal file system (in which case the following files just take up space)# Disclaimer... you should not use this command in a repo that you intend to use with your work as it removes files that attribute the work to their original creators!

find . \( -name "*SECURITY.txt" -o -name "*RELEASE.txt" -o -name "*CHANGELOG.txt" -o -name "*LICENSE.txt" -o -name "*CONTRIBUTING.txt" -name "*HISTORY.md" -o -name "*LICENSE" -o -name "*SECURITY.md" -o -name "*RELEASE.md" -o -name "*CHANGELOG.md" -o -name "*LICENSE.md" -o -name "*CODE_OF_CONDUCT.md" -o -name "\*CONTRIBUTING.md" \) -exec rm -rf -- {} +

In Action:

The following output from my bash shell corresponds to the directory:

bgoonz/bash-commands-walkthrough _Deployment github-pages Navigation Big O notation is the language we use for talking about how long an algorithm takes…_github.com

which was created by running the aforementioned commands in in a perfect copy of this directory:

bgoonz/DS-ALGO-OFFICIAL _Deployment github-pages Navigation Big O notation is the language we use for talking about how long an algorithm takes…_github.com

pwd
/mnt/c/Users/bryan/Downloads/bash-commands/steps/3-clean-up-fluf/DS-ALGO-OFFICIAL-master

find . -empty -type f -print -delete

./CONTENT/DS-n-Algos/File-System/file-utilities/node_modules/line-reader/test/data/empty_file.txt
./CONTENT/DS-n-Algos/_Extra-Practice/free-code-camp/nodejs/http-collect.js
./CONTENT/Resources/Comments/node_modules/mime/.npmignore
./markdown/tree2.md
./node_modules/loadashes6/lodash/README.md
./node_modules/loadashes6/lodash/release.md
./node_modules/web-dev-utils/Markdown-Templates/Markdown-Templates-master/filled-out-readme.md
|01:33:16|bryan@LAPTOP-9LGJ3JGS:[DS-ALGO-OFFICIAL-master] DS-ALGO-OFFICIAL-master_exitstatus:0[╗___________o>

find . -empty -type d -print -delete

|01:33:16|bryan@LAPTOP-9LGJ3JGS:[DS-ALGO-OFFICIAL-master] DS-ALGO-OFFICIAL-master_exitstatus:0[╗___________o>

find . -empty -type d -print -delete
./.git/branches
./.git/objects/info
./.git/refs/tags
|01:33:31|bryan@LAPTOP-9LGJ3JGS:[DS-ALGO-OFFICIAL-master] DS-ALGO-OFFICIAL-master_exitstatus:0[╗___________o>

find . \( -name ".git" -o -name ".gitignore" -o -name ".gitmodules" -o -name ".gitattributes" \) -exec rm -rf -- {} +

The command seen below deletes most SECURITY, RELEASE, CHANGELOG, LICENSE, CONTRIBUTING, & HISTORY files that take up pointless space in repo's you wish to keep exclusively for your own reference.

!!!Use with caution as this command removes the attribution of the work from it's original authors!!!!!

!!!Use with caution as this command removes the attribution of the work from it's original authors!!!!! !!!Use with caution as this command removes the attribution of the work from it's original authors!!!!!find . $ -name "*SECURITY.txt" -o -name "*RELEASE.txt" -o -name "*CHANGELOG.txt" -o -name "*LICENSE.txt" -o -name "*CONTRIBUTING.txt" -name "*HISTORY.md" -o -name "*LICENSE" -o -name "*SECURITY.md" -o -name "*RELEASE.md" -o -name "*CHANGELOG.md" -o -name "*LICENSE.md" -o -name "*CODE_OF_CONDUCT.md" -o -name "*CONTRIBUTING.md" $ -exec rm -rf -- {} +

4.) Generate index.html file that links to all other files in working directory:

#!/bin/sh
# find ./ | grep -i "\.*$" >files
find ./ | sed -E -e 's/([^ ]+[ ]+){8}//' | grep -i "\.*$">files
listing="files"
out=""
html="index.html"
out="basename $out.html"
html="index.html"
cmd() {
  echo '  <!DOCTYPE html>'
  echo '<html>'
  echo '<head>'
  echo '  <meta http-equiv="Content-Type" content="text/html">'
  echo '  <meta name="Author" content="Bryan Guner">'
  echo '<link rel="stylesheet" href="./assets/prism.css">'
  echo ' <link rel="stylesheet" href="./assets/style.css">'
  echo ' <script async defer src="./assets/prism.js"></script>'
  echo "  <title> directory </title>"
  echo ""
  echo '<style>'
echo '    a {'
echo '      color: black;'
echo '    }'
echo ''
echo '    li {'
echo '      border: 1px solid black !important;'
echo '      font-size: 20px;'
echo '      letter-spacing: 0px;'
echo '      font-weight: 700;'
echo '      line-height: 16px;'
echo '      text-decoration: none !important;'
echo '      text-transform: uppercase;'
echo '      background: #194ccdaf !important;'
echo '      color: black !important;'
echo '      border: none;'
echo '      cursor: pointer;'
echo '      justify-content: center;'
echo '      padding: 30px 60px;'
echo '      height: 48px;'
echo '      text-align: center;'
echo '      white-space: normal;'
echo '      border-radius: 10px;'
echo '      min-width: 45em;'
echo '      padding: 1.2em 1em 0;'
echo '      box-shadow: 0 0 5px;'
echo '      margin: 1em;'
echo '      display: grid;'
echo '      -webkit-border-radius: 10px;'
echo '      -moz-border-radius: 10px;'
echo '      -ms-border-radius: 10px;'
echo '      -o-border-radius: 10px;'
echo '    }'
echo '  </style>'
  echo '</head>'
  echo '<body>'
  echo ""
  # continue with the HTML stuff
  echo ""
  echo ""
  echo "<ul>"
  awk '{print "<li><a href=\""$1"\">",$1,"&nbsp;</a></li>"}' $listing
  # awk '{print "<li>"};
  #  {print " <a href=\""$1"\">",$1,"</a></li>&nbsp;"}' \ $listing
  echo ""
  echo "</ul>"
  echo "</body>"
  echo "</html>"
}
cmd $listing --sort=extension >>$html

In Action:

I will use this copy of my Data Structures Practice Site to demonstrate the result:

side-projects-42/DS-Bash-Examples-Deploy _Deployment github-pages Navigation Big O notation is the language we use for talking about how long an algorithm takes…_github.com

#### The result is a index.html file that contains a list of links to each file in the directory:

index.html _CONTENT/DS-n-Algos/_quirky-meninsky-4181b5.netlify.app

5.) Download all links to a files of a specified extension on a user provided (url) webpage:

wget -r -A.pdf https://overapi.com/gitwget --wait=2 --level=inf --limit-rate=20K --recursive --page-requisites --user-agent=Mozilla --no-parent --convert-links --adjust-extension --no-clobber -e robots=off

6.)Recursively remove lines of text containing the string badFolder from files in the working directory.

find . -type f -exec sed -i '/badFolder/d' ./* {} \;

# OR

find . -name 'result.md'  -type f -exec sed -i '/badFolder/d' ./* {} \;

As an example I will run this command on a file containing the text:

Hacks Blog

Read more at hacks.mozilla.org

badFolder

badFolder Implementing Private Fields for JavaScript

When implementing a language feature for JavaScript, an implementer must make decisions about how the language in the specification maps to the implementation. Private fields is an example of where the specification language and implementation reality diverge, at least in SpiderMonkey– the JavaScript engine which powers Firefox. To understand more, I'll explain what private fields are, a couple of models for thinking about them, and explain why our implementation diverges from the specification language.The post Implementing Private Fields for JavaScript appeared first on Mozilla Hacks - the Web developer blog.

Posted Tuesday, June 8, 2021 by Matthew Gaudet

Looking fine with Firefox 89

Firefox 89 has smartened up and brings with it a slimmed-down, slightly more minimalist interface.badFolder Along with this new look, we get some great styling features including a force-colours feature for media queries and better control over how fonts are displayed. The long-awaited top-level await keyword for JavaScript modules is now enabled, as well as the PerformanceEventTiming interface, which is another addition to the performance suite of APIs: 89 really has been working out!The post Looking fine with Firefox 89 appeared first on Mozilla Hacks - the Web developer blog.

badFolder

Posted Tuesday, June 1, 2021 by Chris Mills

badFolder

Improving Firefox stability on Linux

Roughly a year ago at Mozilla we started an effort to improve Firefox stability on Linux. This effort quickly became an example of good synergies between FOSS projects.The post Improving Firefox stability on Linux appeared first on Mozilla Hacks - the Web developer blog.

Posted Wednesday, May 19, 2021 by Gabriele Svelto badFolder

Introducing Firefox's new Site Isolation Security Architecture

Like any web browser, Firefox loads code from untrusted and potentially hostile websites and runs it on your computer. To protect you against new types of attacks from malicious sites and to meet the security principles of Mozilla, we set out to redesign Firefox on desktop.The post Introducing Firefox's new Site Isolation Security Architecture appeared first on Mozilla Hacks - the Web developer blog.

Posted Tuesday, May 18, 2021 by Anny Gakhokidze

Pyodide Spin Out and 0.17 Release

We are happy to announce that Pyodide has become an independent and community-driven project. We are also pleased to announce the 0.17 release for Pyodide with many new features and improvements. Pyodide consists of the CPython 3.8 interpreter compiled to WebAssembly which allows Python to run in the browser.The post Pyodide Spin Out and 0.17 Release appeared first on Mozilla Hacks - the Web developer blog. badFolder

Posted Thursday, April 22, 2021 by Teon Brooks

I modified the command slightly to apply only to files called 'result.md':

Hacks Blog

Read more at hacks.mozilla.org

When implementing a language feature for JavaScript, an implementer must make decisions about how the language in the specification maps to the implementation. Private fields is an example of where the specification language and implementation reality diverge, at least in SpiderMonkey– the JavaScript engine which powers Firefox. To understand more, I'll explain what private fields are, a couple of models for thinking about them, and explain why our implementation diverges from the specification language.The post Implementing Private Fields for JavaScript appeared first on Mozilla Hacks - the Web developer blog.

Posted Tuesday, June 8, 2021 by Matthew Gaudet

Looking fine with Firefox 89

Posted Tuesday, June 1, 2021 by Chris Mills

Improving Firefox stability on Linux

Roughly a year ago at Mozilla we started an effort to improve Firefox stability on Linux. This effort quickly became an example of good synergies between FOSS projects.The post Improving Firefox stability on Linux appeared first on Mozilla Hacks - the Web developer blog.

Introducing Firefox's new Site Isolation Security Architecture

Like any web browser, Firefox loads code from untrusted and potentially hostile websites and runs it on your computer. To protect you against new types of attacks from malicious sites and to meet the security principles of Mozilla, we set out to redesign Firefox on desktop.The post Introducing Firefox's new Site Isolation Security Architecture appeared first on Mozilla Hacks - the Web developer blog.

Posted Tuesday, May 18, 2021 by Anny Gakhokidze

Pyodide Spin Out and 0.17 Release

Posted Thursday, April 22, 2021 by Teon Brooks

the test.txt and result.md files can be found here:

bgoonz/bash-commands-walkthrough _to accompany the medium article I am writing. Contribute to bgoonz/bash-commands-walkthrough development by creating an…_github.com

7.) Execute command recursively:

Here I have modified the command I wish to run recursively to account for the fact that the 'find' command already works recursively, by appending the -maxdepth 1 flag…

That way, if the command affects the more deeply nested folders we know the outer RecurseDirs function we are using to run the _find/pandoc_** line once in every subfolder of the working directory… is working properly!**

**Run in the folder shown to the left… we would expect every .md file to be accompanied by a newly generated html file by the same name.**

The results of said operation can be found in the following directory

In Action:

🢃 Below 🢃

The final result is:

If you want to run any bash script recursively all you have to do is substitue out line #9 with the command you want to run once in every sub-folder.

function RecurseDirs ()
{
    oldIFS=$IFS
    IFS=$'\n'
    for f in "$@"
    do

#Replace the line below with your own command!

#find ./ -iname "*.md" -maxdepth 1 -type f -exec sh -c 'pandoc --standalone "${0}" -o "${0%.md}.html"' {} \;

#####################################################
# YOUR CODE BELOW!

#####################################################

if [[ -d "${f}" ]]; then
            cd "${f}"
            RecurseDirs $(ls -1 ".")
            cd ..
        fi
    done
    IFS=$oldIFS
}
RecurseDirs "./"

TBC….

Here are some of the other commands I will cover in greater detail… at a later time:

9. Copy any text between <script> tags in a file called example.html to be inserted into a new file: out.js

sed -n -e '/<script>/,/<\/script>/p' example.html >out.js

10. Recursively Delete node_modules folders

find . -name 'node_modules' -type d -print -prune -exec rm -rf '{}' +

11. Sanatize file and folder names to remove illegal characters and reserved words.

sanitize() {
  shopt -s extglob;

  filename=$(basename "$1")
  directory=$(dirname "$1")

  filename_clean=$(echo "$filename" | sed -e 's/[\\/:\*\?"<>\|\x01-\x1F\x7F]//g' -e 's/^\(nul\|prn\|con\|lpt[0-9]\|com[0-9]\|aux\)\(\.\|$\)//i' -e 's/^\.*$//' -e 's/^$/NONAME/')

  if (test "$filename" != "$filename_clean")
  then
    mv -v "$1" "$directory/$filename_clean"
  fi
}

export -f sanitize

sanitize_dir() {
  find "$1" -depth -exec bash -c 'sanitize "$0"' {} \;

}

sanitize_dir '/path/to/somewhere'

12. Start postgresql in terminal

sudo -u postgres psql

13. Add closing body and script tags to each html file in working directory.

for f in * ; do
  mv "$f" "$f.html"
doneecho "<form>
 <input type="button" value="Go back!" onclick="history.back()">
</form>
  </body></html>" | tee -a *.html

14. Batch Download Videos

#!/bin/bash

link="#insert url here#"
#links were a set of strings with just the index of the video as the variable

num=3
#first video was numbered 3 - weird.

ext=".mp4"

while [ $num -le 66 ]
do
      wget $link$num$ext -P ~/Downloads/
      num=$(($num+1))
done

15. Change File Extension from '.txt' to .doc for all files in working directory.

sudo apt install rename

rename 's/\.txt$/.doc/' *.txt

16. Recursivley change any file with extension .js.download to .js

find . -name "*.\.js\.download" -exec rename 's/\.js\.download$/.js/' '{}' +

17. Copy folder structure including only files of a specific extension into an ouput Folder

find . -name '*.md' | cpio -pdm './../outputFolder'

Discover More:

Web-Dev-Hub _Memoization, Tabulation, and Sorting Algorithms by Example Why is looking at runtime not a reliable method of…_bgoonz-blog.netlify.app

Part 2 of this series:

Medium Continued!!!medium.com

By Bryan Guner on June 29, 2021.

Canonical link

Exported from Medium on August 31, 2021.

Resources:

holy grail

1. Remove spaces from file and folder names and then remove numbers from files and folder names....

Description: need to : `sudo apt install rename`

code:

find . -name "* *" -type d | rename 's/ /_/g'
find . -name "* *" -type f | rename 's/ /_/g'

```sh
find $dir -type f | sed 's|\(.*/\)[^A-Z]*\([A-Z].*\)|mv \"&\" \"\1\2\"|' | sh

find $dir -type d | sed 's|\(.*/\)[^A-Z]*\([A-Z].*\)|mv \"&\" \"\1\2\"|' | sh

for i in *.html; do mv "$i" "${i%-*}.html"; done

for i in *.*; do mv "$i" "${i%-*}.${i##*.}"; done

---
### Description: combine the contents of every file in the contaning directory.


>Notes: this includes the contents of the file it's self...


###### code:


```js
//APPEND-DIR.js
const fs = require('fs');
let cat = require('child_process')
  .execSync('cat *')
  .toString('UTF-8');
fs.writeFile('output.md', cat, err => {
  if (err) throw err;
});

2. Download Website Using Wget:

Description:

code:

wget --limit-rate=200k --no-clobber --convert-links --random-wait -r -p -E -e robots=off -U mozilla https://bootcamp42.gitbook.io/python/

3. Clean Out Messy Git Repo:

code:


find . -empty -type d -print -delete


find . \( -name ".git" -o -name ".gitignore" -o -name ".gitmodules" -o -name ".gitattributes" \) -exec rm -rf -- {} +


find . \( -name "*SECURITY.txt" -o -name "*RELEASE.txt" -o  -name "*CHANGELOG.txt" -o -name "*LICENSE.txt" -o -name "*CONTRIBUTING.txt" -name "*HISTORY.md" -o -name "*LICENSE" -o -name "*SECURITY.md" -o -name "*RELEASE.md" -o  -name "*CHANGELOG.md" -o -name "*LICENSE.md" -o -name "*CODE_OF_CONDUCT.md" -o -name "*CONTRIBUTING.md" \) -exec rm -rf -- {} +

4. clone all of a user's git repositories

Description: clone all of a user or organization's git repositories.

code:

Generalized:



CNTX={users|orgs}; NAME={username|orgname}; PAGE=1
curl "https://api.github.com/$CNTX/$NAME/repos?page=$PAGE&per_page=100" |
  grep -e 'git_url*' |
  cut -d \" -f 4 |
  xargs -L1 git clone

Clone all Git User

CNTX={users}; NAME={bgoonz}; PAGE=1
curl "https://api.github.com/$CNTX/$NAME/repos?page=$PAGE&per_page=200"?branch=master |
  grep -e 'git_url*' |
  cut -d \" -f 4 |
  xargs -L1 git clone

Clone all Git Organization:

CNTX={organizations}; NAME={TheAlgorithms}; PAGE=1
curl "https://api.github.com/$CNTX/$NAME/repos?page=$PAGE&per_page=200"?branch=master |
  grep -e 'git_url*' |
  cut -d \" -f 4 |
  xargs -L1 git clone

5. Git Workflow

Description:

code:

git pull
git init
git add .
git commit -m"update"
git push -u origin master

git init
git add .
git commit -m"update"
git push -u origin main

git init
git add .
git commit -m"update"
git push -u origin bryan-guner

git init
git add .
git commit -m"update"
git push -u origin gh-pages

git init
git add .
git commit -m"update"
git push -u origin preview

6. Recursive Unzip In Place

Description: recursively unzips folders and then deletes the zip file by the same name.

code:

find . -name "*.zip" | while read filename; do unzip -o -d "`dirname "$filename"`" "$filename"; done;



find . -name "*.zip" -type f -print -delete

7. git pull keeping local changes:

Description:

code:


git stash
git pull
git stash pop

8. Prettier Code Formatter:

Description:

code:

sudo npm i prettier -g

prettier --write .

9. Pandoc

Description:

code:

find ./ -iname "*.md" -type f -exec sh -c 'pandoc --standalone "${0}" -o "${0%.md}.html"' {} \;



find ./ -iname "*.html" -type f -exec sh -c 'pandoc --wrap=none --from html --to markdown_strict "${0}" -o "${0%.html}.md"' {} \;



find ./ -iname "*.docx" -type f -exec sh -c 'pandoc "${0}" -o "${0%.docx}.md"' {} \;

10. Gitpod Installs

Description:

code:

sudo apt install tree
sudo apt install pandoc -y
sudo apt install rename -y
sudo apt install black -y
sudo apt install wget -y
npm i lebab -g
npm i prettier -g
npm i npm-recursive-install -g

black .

prettier --write .
npm-recursive-install

11. Repo Utils Package:

Description: my standard repo utis package

code:

npm i @bgoonz11/repoutils

12. Unix Tree Package Usage:

Description:

code:

tree -d -I  'node_modules'

tree  -I  'node_modules'

tree -f  -I  'node_modules' >TREE.md

tree -f -L 2  >README.md

tree -f  -I  'node_modules' >listing-path.md


tree -f  -I  'node_modules' -d >TREE.md

tree -f >README.md

13. Find & Replace string in file & folder names recursively..

Description:

code:

find . -type f -exec rename 's/string1/string2/g' {} +


find . -type d -exec rename 's/-master//g' {} +


find . -type f -exec rename 's/\.download//g' {} +




find . -type d -exec rename 's/-main//g' {} +



rename 's/\.js\.download$/.js/' *.js\.download


rename 's/\.html\.markdown$/.md/' *.html\.markdown


find . -type d -exec rename 's/es6//g' {} +

14. Remove double extensions :

Description:

code:

#!/bin/bash

for file in *.md.md
do
    mv "${file}" "${file%.md}"
done

#!/bin/bash

for file in *.html.html
do
    mv "${file}" "${file%.html}"
done


#!/bin/bash

for file in *.html.png
do
    mv "${file}" "${file%.png}"
done

for file in *.jpg.jpg
do
    mv "${file}" "${file%.png}"
done

15. Truncate folder names down to 12 characters:

Description:

code:

for d in ./*; do mv $d ${d:0:12}; done

16.Appendir.js

Description: combine the contents of every file in the contaning directory.

code:

//APPEND-DIR.js
const fs = require('fs');
let cat = require('child_process').execSync('cat *').toString('UTF-8');
fs.writeFile('output.md', cat, (err) => {
    if (err) throw err;
});

17. Replace space in filename with underscore

Description: followed by replace `'#' with '_'` in directory name

code:

find . -name "* *" -type f | rename 's/_//g'

find . -name "* *" -type d | rename 's/#/_/g'

18. Filter & delete files by name and extension

Description:

code:

find . -name '.bin' -type d -prune -exec rm -rf '{}' +

find . -name '*.html' -type d -prune -exec rm -rf '{}' +

find . -name 'nav-index' -type d -prune -exec rm -rf '{}' +

find . -name 'node-gyp' -type d -prune -exec rm -rf '{}' +

find . -name 'deleteme.txt' -type f -prune -exec rm -rf '{}' +

find . -name 'right.html' -type f -prune -exec rm -rf '{}' +

find . -name 'left.html' -type f -prune -exec rm -rf '{}' +

19. Remove lines containing string:

Description:

sudo sed -i '/\.js/!d' ./*scrap2.md

code:

sudo sed -i '/githubusercontent/d' ./*sandbox.md


sudo sed -i '/githubusercontent/d' ./*scrap2.md



sudo sed -i '/github\.com/d' ./*out.md


sudo sed -i '/author/d' ./*

20. Remove duplicate lines from a text file

Description:

Now, let's understand the use of this with the help of an example. Suppose you have a text file named kt.txt which contains repeated lines that needs to be omitted. This can simply be done with uniq.

code:

sudo apt install uniq
uniq -u input.txt output.txt

21. Remove lines containing string:

Description:

code:

sudo sed -i '/githubusercontent/d' ./*sandbox.md


sudo sed -i '/githubusercontent/d' ./*scrap2.md


sudo sed -i '/github\.com/d' ./*out.md

---
title: add_days
tags: date,intermediate
firstSeen: 2020-10-28T16:19:04+02:00
lastUpdated: 2020-10-28T16:19:04+02:00
---

sudo sed -i '/title:/d' ./*output.md
sudo sed -i '/firstSeen/d' ./*output.md
sudo sed -i '/lastUpdated/d' ./*output.md
sudo sed -i '/tags:/d' ./*output.md

sudo sed -i '/badstring/d' ./*


sudo sed -i '/stargazers/d' ./repo.txt
sudo sed -i '/node_modules/d' ./index.html
sudo sed -i '/right\.html/d' ./index.html
sudo sed -i '/right\.html/d' ./right.html

22. Zip directory excluding .git and node_modules all the way down (Linux)

Description:

code:


#!/bin/bash
TSTAMP=`date '+%Y%m%d-%H%M%S'`
zip -r $1.$TSTAMP.zip $1 -x "**.git/*" -x "**node_modules/*" `shift; echo $@;`

printf "\nCreated: $1.$TSTAMP.zip\n"

# usage:
# - zipdir thedir
# - zip thedir -x "**anotherexcludedsubdir/*"    (important the double quotes to prevent glob expansion)

# if in windows/git-bash, add 'zip' command this way:
# https://stackoverflow.com/a/55749636/1482990

23. Delete files containing a certain string:

Description:

code:

find . | xargs grep -l www.redhat.com | awk '{print "rm "$1}' > doit.sh
vi doit.sh // check for murphy and his law
source doit.sh

24.

Description:

code:

#!/bin/sh

# find ./ | grep -i "\.*$" >files
find ./ | sed -E -e 's/([^ ]+[ ]+){8}//' | grep -i "\.*$">files
listing="files"

out=""

html="sitemap.html"
out="basename $out.html"
html="sitemap.html"
cmd() {

  echo '  <!DOCTYPE html>'
  echo '<html>'
  echo '<head>'

  echo '  <meta http-equiv="Content-Type" content="text/html">'

  echo '  <meta name="Author" content="Bryan Guner">'
  echo '<link rel="stylesheet" href="./assets/prism.css">'
  echo ' <link rel="stylesheet" href="./assets/style.css">'
  echo ' <script async defer src="./assets/prism.js"></script>'

  echo "  <title> directory </title>"
    echo '<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/bgoonz/GIT-CDN-FILES/mdn-article.css">'
  echo '<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/bgoonz/GIT-CDN-FILES/markdown-to-html-style.css">'
  echo ""
  echo '<style>'


echo '    a {'
echo '      color: black;'
echo '    }'
echo ''
echo '    li {'
echo '      border: 1px solid black !important;'
echo '      font-size: 20px;'
echo '      letter-spacing: 0px;'
echo '      font-weight: 700;'
echo '      line-height: 16px;'
echo '      text-decoration: none !important;'
echo '      text-transform: uppercase;'
echo '      background: #194ccdaf !important;'
echo '      color: black !important;'
echo '      border: none;'
echo '      cursor: pointer;'
echo '      justify-content: center;'
echo '      padding: 30px 60px;'
echo '      height: 48px;'
echo '      text-align: center;'
echo '      white-space: normal;'
echo '      border-radius: 10px;'
echo '      min-width: 45em;'
echo '      padding: 1.2em 1em 0;'
echo '      box-shadow: 0 0 5px;'
echo '      margin: 1em;'
echo '      display: grid;'
echo '      -webkit-border-radius: 10px;'
echo '      -moz-border-radius: 10px;'
echo '      -ms-border-radius: 10px;'
echo '      -o-border-radius: 10px;'
echo '    }'
echo '  </style>'
  echo '</head>'

  echo '<body>'

  echo ""

  # continue with the HTML stuff

  echo ""

  echo ""

  echo "<ul>"

  awk '{print "<li><a href=\""$1"\">",$1,"&nbsp;</a></li>"}' $listing

  # awk '{print "<li>"};

  # 	{print " <a href=\""$1"\">",$1,"</a></li>&nbsp;"}' \ $listing

  echo ""

  echo "</ul>"

  echo "</body>"

  echo "</html>"

}

cmd $listing --sort=extension >>$html

25. Index of Iframes

Description: Creates an index.html file that contains all the files in the working directory or any of it's sub folders as iframes instead of anchor tags.

code:


#!/bin/sh

# find ./ | grep -i "\.*$" >files
find ./ | sed -E -e 's/([^ ]+[ ]+){8}//' | grep -i "\.*$">files
listing="files"

out=""

html="index.html"
out="basename $out.html"
html="index.html"
cmd() {

  echo '  <!DOCTYPE html>'
  echo '<html>'
  echo '<head>'

  echo '  <meta http-equiv="Content-Type" content="text/html">'

  echo '  <meta name="Author" content="Bryan Guner">'
  echo '<link rel="stylesheet" href="./assets/prism.css">'
  echo ' <link rel="stylesheet" href="./assets/style.css">'
  echo ' <script async defer src="./assets/prism.js"></script>'

  echo "  <title> directory </title>"

  echo ""
  echo '<style>'


echo '    a {'
echo '      color: black;'
echo '    }'
echo ''
echo '    li {'
echo '      border: 1px solid black !important;'
echo '      font-size: 20px;'
echo '      letter-spacing: 0px;'
echo '      font-weight: 700;'
echo '      line-height: 16px;'
echo '      text-decoration: none !important;'
echo '      text-transform: uppercase;'
echo '      background: #194ccdaf !important;'
echo '      color: black !important;'
echo '      border: none;'
echo '      cursor: pointer;'
echo '      justify-content: center;'
echo '      padding: 30px 60px;'
echo '      height: 48px;'
echo '      text-align: center;'
echo '      white-space: normal;'
echo '      border-radius: 10px;'
echo '      min-width: 45em;'
echo '      padding: 1.2em 1em 0;'
echo '      box-shadow: 0 0 5px;'
echo '      margin: 1em;'
echo '      display: grid;'
echo '      -webkit-border-radius: 10px;'
echo '      -moz-border-radius: 10px;'
echo '      -ms-border-radius: 10px;'
echo '      -o-border-radius: 10px;'
echo '    }'
echo '  </style>'
  echo '</head>'

  echo '<body>'

  echo ""

  # continue with the HTML stuff

  echo ""

  echo ""

  echo "<ul>"

  awk '{print "<iframe src=\""$1"\">","</iframe>"}' $listing

  # awk '{print "<li>"};

  # 	{print " <a href=\""$1"\">",$1,"</a></li>&nbsp;"}' \ $listing

  echo ""

  echo "</ul>"

  echo "</body>"

  echo "</html>"

}

cmd $listing --sort=extension >>$html

26. Filter Corrupted Git Repo For Troublesome File:

Description:

code:

git filter-branch --index-filter 'git rm -r --cached --ignore-unmatch assets/_index.html' HEAD

27. OVERWRITE LOCAL CHANGES:

Description:

Important: If you have any local changes, they will be lost. With or without --hard option, any local commits that haven't been pushed will be lost.[*] If you have any files that are not tracked by Git (e.g. uploaded user content), these files will not be affected.

code:

git fetch --all
# Backup your current branch:

git branch backup-master
# Then, you have two options:

git reset --hard origin/master
# OR If you are on some other branch:

git reset --hard origin/<branch_name>
# Explanation:
# git fetch downloads the latest from remote without trying to merge or rebase anything.

# Then the git reset resets the master branch to what you just fetched. The --hard option changes all the files in your working tree to match the files in origin/master
git fetch --all
git reset --hard origin/master

28. Remove Submodules:

Description: To remove a submodule you need to:

code:

git submodule deinit

29. GET GISTS

Description:

code:

sudo apt install wget



wget -q -O - https://api.github.com/users/bgoonz/gists | grep raw_url | awk -F\" '{print $4}' | xargs -n3 wget


wget -q -O - https://api.github.com/users/amitness/gists | grep raw_url | awk -F\" '{print $4}' | xargs -n3 wget


wget -q -O - https://api.github.com/users/drodsou/gists | grep raw_url | awk -F\" '{print $4}' | xargs -n1 wget

wget -q -O - https://api.github.com/users/thomasmb/gists | grep raw_url | awk -F\" '{print $4}' | xargs -n1 wget

30. Remove Remote OriginL

Description:

code:

git remote remove origin

31. just clone .git folder:

Description:

code:


git clone --bare --branch=master --single-branch https://github.com/bgoonz/My-Web-Dev-Archive.git

32. Undo recent pull request:

Description:

code:

git reset --hard master@{"10 minutes ago"}

33. Lebab

Description: ES5 --> ES6

code:

# Safe:

 lebab --replace ./ --transform arrow
 lebab --replace ./ --transform arrow-return
 lebab --replace ./ --transform for-of
 lebab --replace ./ --transform for-each
 lebab --replace ./ --transform arg-rest
 lebab --replace ./ --transform arg-spread
 lebab --replace ./ --transform obj-method
 lebab --replace ./ --transform obj-shorthand
 lebab --replace ./ --transform multi-var


# ALL:


lebab --replace ./ --transform obj-method
lebab --replace ./ --transform class
lebab --replace ./ --transform arrow
lebab --replace ./ --transform let
lebab --replace ./ --transform arg-spread
lebab --replace ./ --transform arg-rest
lebab --replace ./ --transform for-each
lebab --replace ./ --transform for-of
lebab --replace ./ --transform commonjs
lebab --replace ./ --transform exponent
lebab --replace ./ --transform multi-var
lebab --replace ./ --transform template
lebab --replace ./ --transform default-param
lebab --replace ./ --transform  destruct-param
lebab --replace ./ --transform includes
lebab --replace ./ --transform obj-method
lebab --replace ./ --transform class
lebab --replace ./ --transform arrow
lebab --replace ./ --transform arg-spread
lebab --replace ./ --transform arg-rest
lebab --replace ./ --transform for-each
lebab --replace ./ --transform for-of
lebab --replace ./ --transform commonjs
lebab --replace ./ --transform exponent
lebab --replace ./ --transform multi-var
lebab --replace ./ --transform template
lebab --replace ./ --transform default-param
lebab --replace ./ --transform  destruct-param
lebab --replace ./ --transform includes

34. Troubleshoot Ubuntu Input/Output Error

Description: Open Powershell as Administrator...

code:

 wsl.exe --shutdown

 Get-Service LxssManager | Restart-Service

35. Export Medium as Markdown

Description:

code:

npm i mediumexporter -g


mediumexporter https://medium.com/codex/fundamental-data-structures-in-javascript-8f9f709c15b4 >ds.md

36. Delete files in violation of a given size range (100MB for git)

Description:

code:

find . -size +75M -a -print -a -exec rm -f {} \;




find . -size +98M -a -print -a -exec rm -f {} \;

37. download all links of given file type

Description:

code:


wget -r -A.pdf https://overapi.com/git

38. Kill all node processes

Description:

code:

killall -s KILL node

39. Remove string from file names recursively

Description: In the example below I am using this command to remove the string "-master" from all file names in the working directory and all of it's sub directories.

code:

find <mydir> -type f -exec sed -i 's/<string1>/<string2>/g' {} +




find . -type f -exec rename 's/-master//g' {} +

find <mydir> -type d -exec sed -i 's/<string1>/<string2>/g' {} +




find . -type d -exec rename 's/-master//g' {} +

40. Remove spaces from file and folder names recursively

Description: replaces spaces in file and folder names with an `_` underscore

code:

find . -name "* *" -type d | rename 's/ /_/g'
find . -name "* *" -type f | rename 's/ /_/g'

41. Zip Each subdirectories in a given directory into their own zip file

Description:

code:

for i in */; do zip -r "${i%/}.zip" "$i"; done

42.

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91. Unzip PowerShell

Description:

code:

PARAM (
    [string] $ZipFilesPath = "./",
    [string] $UnzipPath = "./RESULT"
)

$Shell = New-Object -com Shell.Application
$Location = $Shell.NameSpace($UnzipPath)

$ZipFiles = Get-Childitem $ZipFilesPath -Recurse -Include *.ZIP

$progress = 1
foreach ($ZipFile in $ZipFiles) {
    Write-Progress -Activity "Unzipping to $($UnzipPath)" -PercentComplete (($progress / ($ZipFiles.Count + 1)) * 100) -CurrentOperation $ZipFile.FullName -Status "File $($Progress) of $($ZipFiles.Count)"
    $ZipFolder = $Shell.NameSpace($ZipFile.fullname)


    $Location.Copyhere($ZipFolder.items(), 1040) # 1040 - No msgboxes to the user - http://msdn.microsoft.com/en-us/library/bb787866%28VS.85%29.aspx
    $progress++
}

92. return to bash from zsh

Description:

code:

 sudo apt --purge remove zsh

93. Symbolic Link

Description: to working directory

code:

ln -s "$(pwd)" ~/NameOfLink

ln -s "$(pwd)" ~/Downloads

94. auto generate readme

Description: rename existing readme to blueprint.md

code:

npx @appnest/readme generate

95. Log into postgres:

Description:

code:

sudo -u postgres psql

Description:

code:

https://www.youtube.com/channel/UC1HDa0wWnIKUf-b4yY9JecQ?sub_confirmation=1

97. Embed Repl.it In Medium Post:

code:

https://repl.it/@bgoonz/Data-Structures-Algos-Codebase?lite=true&amp;referrer=https%3A%2F%2Fbryanguner.medium.com


https://repl.it/@bgoonz/node-db1-project?lite=true&amp;referrer=https%3A%2F%2Fbryanguner.medium.com

https://repl.it/@bgoonz/interview-prac?lite=true&amp;referrer=https%3A%2F%2Fbryanguner.medium.com


https://repl.it/@bgoonz/Database-Prac?lite=true&amp;referrer=https%3A%2F%2Fbryanguner.medium.com

98.

Description:

code:


find . -name *right.html  -type f -exec sed -i 's/target="_parent"//g' {} +


find . -name *right.html  -type f -exec sed -i 's/target="_parent"//g' {} +

99. Cheat Sheet

Description:

code:

#!/bin/bash
##############################################################################
# SHORTCUTS and HISTORY
##############################################################################

CTRL+A  # move to beginning of line
CTRL+B  # moves backward one character
CTRL+C  # halts the current command
CTRL+D  # deletes one character backward or logs out of current session, similar to exit
CTRL+E  # moves to end of line
CTRL+F  # moves forward one character
CTRL+G  # aborts the current editing command and ring the terminal bell
CTRL+H  # deletes one character under cursor (same as DELETE)
CTRL+J  # same as RETURN
CTRL+K  # deletes (kill) forward to end of line
CTRL+L  # clears screen and redisplay the line
CTRL+M  # same as RETURN
CTRL+N  # next line in command history
CTRL+O  # same as RETURN, then displays next line in history file
CTRL+P  # previous line in command history
CTRL+Q  # resumes suspended shell output
CTRL+R  # searches backward
CTRL+S  # searches forward or suspends shell output
CTRL+T  # transposes two characters
CTRL+U  # kills backward from point to the beginning of line
CTRL+V  # makes the next character typed verbatim
CTRL+W  # kills the word behind the cursor
CTRL+X  # lists the possible filename completions of the current word
CTRL+Y  # retrieves (yank) last item killed
CTRL+Z  # stops the current command, resume with fg in the foreground or bg in the background

ALT+B   # moves backward one word
ALT+D   # deletes next word
ALT+F   # moves forward one word
ALT+H   # deletes one character backward
ALT+T   # transposes two words
ALT+.   # pastes last word from the last command. Pressing it repeatedly traverses through command history.
ALT+U   # capitalizes every character from the current cursor position to the end of the word
ALT+L   # uncapitalizes every character from the current cursor position to the end of the word
ALT+C   # capitalizes the letter under the cursor. The cursor then moves to the end of the word.
ALT+R   # reverts any changes to a command you've pulled from your history if you've edited it.
ALT+?   # list possible completions to what is typed
ALT+^   # expand line to most recent match from history

CTRL+X then (   # start recording a keyboard macro
CTRL+X then )   # finish recording keyboard macro
CTRL+X then E   # recall last recorded keyboard macro
CTRL+X then CTRL+E   # invoke text editor (specified by $EDITOR) on current command line then execute resultes as shell commands

BACKSPACE  # deletes one character backward
DELETE     # deletes one character under cursor

history   # shows command line history
!!        # repeats the last command
!<n>      # refers to command line 'n'
!<string> # refers to command starting with 'string'

exit      # logs out of current session


##############################################################################
# BASH BASICS
##############################################################################

env                 # displays all environment variables

echo $SHELL         # displays the shell you're using
echo $BASH_VERSION  # displays bash version

bash                # if you want to use bash (type exit to go back to your previously opened shell)
whereis bash        # locates the binary, source and manual-page for a command
which bash          # finds out which program is executed as 'bash' (default: /bin/bash, can change across environments)

clear               # clears content on window (hide displayed lines)


##############################################################################
# FILE COMMANDS
##############################################################################


ls                            # lists your files in current directory, ls <dir> to print files in a specific directory
ls -l                         # lists your files in 'long format', which contains the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified
ls -a                         # lists all files in 'long format', including hidden files (name beginning with '.')
ln -s <filename> <link>       # creates symbolic link to file
readlink <filename>           # shows where a symbolic links points to
tree                          # show directories and subdirectories in easilly readable file tree
mc                            # terminal file explorer (alternative to ncdu)
touch <filename>              # creates or updates (edit) your file
mktemp -t <filename>            # make a temp file in /tmp/ which is deleted at next boot (-d to make directory)
cat <filename>                # prints file raw content (will not be interpreted)
any_command > <filename>      # '>' is used to perform redirections, it will set any_command's stdout to file instead of "real stdout" (generally /dev/stdout)
more <filename>               # shows the first part of a file (move with space and type q to quit)
head <filename>               # outputs the first lines of file (default: 10 lines)
tail <filename>               # outputs the last lines of file (useful with -f option) (default: 10 lines)
vim <filename>                # opens a file in VIM (VI iMproved) text editor, will create it if it doesn't exist
mv <filename1> <dest>         # moves a file to destination, behavior will change based on 'dest' type (dir: file is placed into dir; file: file will replace dest (tip: useful for renaming))
cp <filename1> <dest>         # copies a file
rm <filename>                 # removes a file
find . -name <name> <type>    # searches for a file or a directory in the current directory and all its sub-directories by its name
diff <filename1> <filename2>  # compares files, and shows where they differ
wc <filename>                 # tells you how many lines, words and characters there are in a file. Use -lwc (lines, word, character) to ouput only 1 of those informations
sort <filename>               # sorts the contents of a text file line by line in alphabetical order, use -n for numeric sort and -r for reversing order.
sort -t -k <filename>         # sorts the contents on specific sort key field starting from 1, using the field separator t.
rev                           # reverse string characters (hello becomes olleh)
chmod -options <filename>     # lets you change the read, write, and execute permissions on your files (more infos: SUID, GUID)
gzip <filename>               # compresses files using gzip algorithm
gunzip <filename>             # uncompresses files compressed by gzip
gzcat <filename>              # lets you look at gzipped file without actually having to gunzip it
lpr <filename>                # prints the file
lpq                           # checks out the printer queue
lprm <jobnumber>              # removes something from the printer queue
genscript                     # converts plain text files into postscript for printing and gives you some options for formatting
dvips <filename>              # prints .dvi files (i.e. files produced by LaTeX)
grep <pattern> <filenames>    # looks for the string in the files
grep -r <pattern> <dir>       # search recursively for pattern in directory
head -n file_name | tail +n   # Print nth line from file.
head -y lines.txt | tail +x   # want to display all the lines from x to y. This includes the xth and yth lines.


##############################################################################
# DIRECTORY COMMANDS
##############################################################################


mkdir <dirname>               # makes a new directory
rmdir <dirname>               # remove an empty directory
rmdir -rf <dirname>           # remove a non-empty directory
mv <dir1> <dir2>              # rename a directory from <dir1> to <dir2>
cd                            # changes to home
cd ..                         # changes to the parent directory
cd <dirname>                  # changes directory
cp -r <dir1> <dir2>           # copy <dir1> into <dir2> including sub-directories
pwd                           # tells you where you currently are
cd ~                          # changes to home.
cd -                          # changes to previous working directory

##############################################################################
# SSH, SYSTEM INFO & NETWORK COMMANDS
##############################################################################


ssh user@host            # connects to host as user
ssh -p <port> user@host  # connects to host on specified port as user
ssh-copy-id user@host    # adds your ssh key to host for user to enable a keyed or passwordless login

whoami                   # returns your username
passwd                   # lets you change your password
quota -v                 # shows what your disk quota is
date                     # shows the current date and time
cal                      # shows the month's calendar
uptime                   # shows current uptime
w                        # displays whois online
finger <user>            # displays information about user
uname -a                 # shows kernel information
man <command>            # shows the manual for specified command
df                       # shows disk usage
du <filename>            # shows the disk usage of the files and directories in filename (du -s give only a total)
last <yourUsername>      # lists your last logins
ps -u yourusername       # lists your processes
kill <PID>               # kills the processes with the ID you gave
killall <processname>    # kill all processes with the name
top                      # displays your currently active processes
lsof                     # lists open files
bg                       # lists stopped or background jobs ; resume a stopped job in the background
fg                       # brings the most recent job in the foreground
fg <job>                 # brings job to the foreground

ping <host>              # pings host and outputs results
whois <domain>           # gets whois information for domain
dig <domain>             # gets DNS information for domain
dig -x <host>            # reverses lookup host
wget <file>              # downloads file

time <command>             # report time consumed by command execution


##############################################################################
# VARIABLES
##############################################################################


varname=value                # defines a variable
varname=value command        # defines a variable to be in the environment of a particular subprocess
echo $varname                # checks a variable's value
echo $$                      # prints process ID of the current shell
echo $!                      # prints process ID of the most recently invoked background job
echo $?                      # displays the exit status of the last command
read <varname>               # reads a string from the input and assigns it to a variable
read -p "prompt" <varname>   # same as above but outputs a prompt to ask user for value
column -t <filename>         # display info in pretty columns (often used with pipe)
let <varname> = <equation>   # performs mathematical calculation using operators like +, -, *, /, %
export VARNAME=value         # defines an environment variable (will be available in subprocesses)

array[0]=valA                # how to define an array
array[1]=valB
array[2]=valC
array=([2]=valC [0]=valA [1]=valB)  # another way
array=(valA valB valC)              # and another

${array[i]}                  # displays array's value for this index. If no index is supplied, array element 0 is assumed
${#array[i]}                 # to find out the length of any element in the array
${#array[@]}                 # to find out how many values there are in the array

declare -a                   # the variables are treated as arrays
declare -f                   # uses function names only
declare -F                   # displays function names without definitions
declare -i                   # the variables are treated as integers
declare -r                   # makes the variables read-only
declare -x                   # marks the variables for export via the environment

${varname:-word}             # if varname exists and isn't null, return its value; otherwise return word
${varname:word}              # if varname exists and isn't null, return its value; otherwise return word
${varname:=word}             # if varname exists and isn't null, return its value; otherwise set it word and then return its value
${varname:?message}          # if varname exists and isn't null, return its value; otherwise print varname, followed by message and abort the current command or script
${varname:+word}             # if varname exists and isn't null, return word; otherwise return null
${varname:offset:length}     # performs substring expansion. It returns the substring of $varname starting at offset and up to length characters

${variable#pattern}          # if the pattern matches the beginning of the variable's value, delete the shortest part that matches and return the rest
${variable##pattern}         # if the pattern matches the beginning of the variable's value, delete the longest part that matches and return the rest
${variable%pattern}          # if the pattern matches the end of the variable's value, delete the shortest part that matches and return the rest
${variable%%pattern}         # if the pattern matches the end of the variable's value, delete the longest part that matches and return the rest
${variable/pattern/string}   # the longest match to pattern in variable is replaced by string. Only the first match is replaced
${variable//pattern/string}  # the longest match to pattern in variable is replaced by string. All matches are replaced

${#varname}                  # returns the length of the value of the variable as a character string

*(patternlist)               # matches zero or more occurrences of the given patterns
+(patternlist)               # matches one or more occurrences of the given patterns
?(patternlist)               # matches zero or one occurrence of the given patterns
@(patternlist)               # matches exactly one of the given patterns
!(patternlist)               # matches anything except one of the given patterns

$(UNIX command)              # command substitution: runs the command and returns standard output


##############################################################################
# FUNCTIONS
##############################################################################


# The function refers to passed arguments by position (as if they were positional parameters), that is, $1, $2, and so forth.
# $@ is equal to "$1" "$2"... "$N", where N is the number of positional parameters. $# holds the number of positional parameters.


function functname() {
  shell commands
}

unset -f functname  # deletes a function definition
declare -f          # displays all defined functions in your login session


##############################################################################
# FLOW CONTROLS
##############################################################################


statement1 && statement2  # and operator
statement1 || statement2  # or operator

-a                        # and operator inside a test conditional expression
-o                        # or operator inside a test conditional expression

# STRINGS

str1 == str2               # str1 matches str2
str1 != str2               # str1 does not match str2
str1 < str2                # str1 is less than str2 (alphabetically)
str1 > str2                # str1 is greater than str2 (alphabetically)
str1 \> str2               # str1 is sorted after str2
str1 \< str2               # str1 is sorted before str2
-n str1                    # str1 is not null (has length greater than 0)
-z str1                    # str1 is null (has length 0)

# FILES

-a file                   # file exists or its compilation is successful
-d file                   # file exists and is a directory
-e file                   # file exists; same -a
-f file                   # file exists and is a regular file (i.e., not a directory or other special type of file)
-r file                   # you have read permission
-s file                   # file exists and is not empty
-w file                   # your have write permission
-x file                   # you have execute permission on file, or directory search permission if it is a directory
-N file                   # file was modified since it was last read
-O file                   # you own file
-G file                   # file's group ID matches yours (or one of yours, if you are in multiple groups)
file1 -nt file2           # file1 is newer than file2
file1 -ot file2           # file1 is older than file2

# NUMBERS

-lt                       # less than
-le                       # less than or equal
-eq                       # equal
-ge                       # greater than or equal
-gt                       # greater than
-ne                       # not equal

if condition
then
  statements
[elif condition
  then statements...]
[else
  statements]
fi

for x in {1..10}
do
  statements
done

for name [in list]
do
  statements that can use $name
done

for (( initialisation ; ending condition ; update ))
do
  statements...
done

case expression in
  pattern1 )
    statements ;;
  pattern2 )
    statements ;;
esac

select name [in list]
do
  statements that can use $name
done

while condition; do
  statements
done

until condition; do
  statements
done

##############################################################################
# COMMAND-LINE PROCESSING CYCLE
##############################################################################


# The default order for command lookup is functions, followed by built-ins, with scripts and executables last.
# There are three built-ins that you can use to override this order: `command`, `builtin` and `enable`.

command  # removes alias and function lookup. Only built-ins and commands found in the search path are executed
builtin  # looks up only built-in commands, ignoring functions and commands found in PATH
enable   # enables and disables shell built-ins

eval     # takes arguments and run them through the command-line processing steps all over again


##############################################################################
# INPUT/OUTPUT REDIRECTORS
##############################################################################


cmd1|cmd2  # pipe; takes standard output of cmd1 as standard input to cmd2
< file     # takes standard input from file
> file     # directs standard output to file
>> file    # directs standard output to file; append to file if it already exists
>|file     # forces standard output to file even if noclobber is set
n>|file    # forces output to file from file descriptor n even if noclobber is set
<> file    # uses file as both standard input and standard output
n<>file    # uses file as both input and output for file descriptor n
n>file     # directs file descriptor n to file
n<file     # takes file descriptor n from file
n>>file    # directs file description n to file; append to file if it already exists
n>&        # duplicates standard output to file descriptor n
n<&        # duplicates standard input from file descriptor n
n>&m       # file descriptor n is made to be a copy of the output file descriptor
n<&m       # file descriptor n is made to be a copy of the input file descriptor
&>file     # directs standard output and standard error to file
<&-        # closes the standard input
>&-        # closes the standard output
n>&-       # closes the ouput from file descriptor n
n<&-       # closes the input from file descripor n

|tee <file># output command to both terminal and a file (-a to append to file)


##############################################################################
# PROCESS HANDLING
##############################################################################


# To suspend a job, type CTRL+Z while it is running. You can also suspend a job with CTRL+Y.
# This is slightly different from CTRL+Z in that the process is only stopped when it attempts to read input from terminal.
# Of course, to interrupt a job, type CTRL+C.

myCommand &  # runs job in the background and prompts back the shell

jobs         # lists all jobs (use with -l to see associated PID)

fg           # brings a background job into the foreground
fg %+        # brings most recently invoked background job
fg %-        # brings second most recently invoked background job
fg %N        # brings job number N
fg %string   # brings job whose command begins with string
fg %?string  # brings job whose command contains string

kill -l               # returns a list of all signals on the system, by name and number
kill PID              # terminates process with specified PID
kill -s SIGKILL 4500  # sends a signal to force or terminate the process
kill -15 913          # Ending PID 913 process with signal 15 (TERM)
kill %1               # Where %1 is the number of job as read from 'jobs' command.

ps           # prints a line of information about the current running login shell and any processes running under it
ps -a        # selects all processes with a tty except session leaders

trap cmd sig1 sig2  # executes a command when a signal is received by the script
trap "" sig1 sig2   # ignores that signals
trap - sig1 sig2    # resets the action taken when the signal is received to the default

disown <PID|JID>    # removes the process from the list of jobs

wait                # waits until all background jobs have finished
sleep <number>      # wait # of seconds before continuing

pv                  # display progress bar for data handling commands. often used with pipe like |pv
yes                 # give yes response everytime an input is requested from script/process


##############################################################################
# TIPS & TRICKS
##############################################################################


# set an alias
cd; nano .bash_profile
> alias gentlenode='ssh admin@gentlenode.com -p 3404'  # add your alias in .bash_profile

# to quickly go to a specific directory
cd; nano .bashrc
> shopt -s cdable_vars
> export websites="/Users/mac/Documents/websites"

source .bashrc
cd $websites


##############################################################################
# DEBUGGING SHELL PROGRAMS
##############################################################################


bash -n scriptname  # don't run commands; check for syntax errors only
set -o noexec       # alternative (set option in script)

bash -v scriptname  # echo commands before running them
set -o verbose      # alternative (set option in script)

bash -x scriptname  # echo commands after command-line processing
set -o xtrace       # alternative (set option in script)

trap 'echo $varname' EXIT  # useful when you want to print out the values of variables at the point that your script exits

function errtrap {
  es=$?
  echo "ERROR line $1: Command exited with status $es."
}

trap 'errtrap $LINENO' ERR  # is run whenever a command in the surrounding script or function exits with non-zero status

function dbgtrap {
  echo "badvar is $badvar"
}

trap dbgtrap DEBUG  # causes the trap code to be executed before every statement in a function or script
# ...section of code in which the problem occurs...
trap - DEBUG  # turn off the DEBUG trap

function returntrap {
  echo "A return occurred"
}

trap returntrap RETURN  # is executed each time a shell function or a script executed with the . or source commands finishes executing

##############################################################################
# COLORS AND BACKGROUNDS
##############################################################################
# note: \e or \x1B also work instead of \033
# Reset
Color_Off='\033[0m' # Text Reset

# Regular Colors
Black='\033[0;30m'  # Black
Red='\033[0;31m'    # Red
Green='\033[0;32m'  # Green
Yellow='\033[0;33m' # Yellow
Blue='\033[0;34m'   # Blue
Purple='\033[0;35m' # Purple
Cyan='\033[0;36m'   # Cyan
White='\033[0;97m'  # White

# Additional colors
LGrey='\033[0;37m'  # Ligth Gray
DGrey='\033[0;90m'  # Dark Gray
LRed='\033[0;91m'   # Ligth Red
LGreen='\033[0;92m' # Ligth Green
LYellow='\033[0;93m'# Ligth Yellow
LBlue='\033[0;94m'  # Ligth Blue
LPurple='\033[0;95m'# Light Purple
LCyan='\033[0;96m'  # Ligth Cyan


# Bold
BBlack='\033[1;30m' # Black
BRed='\033[1;31m'   # Red
BGreen='\033[1;32m' # Green
BYellow='\033[1;33m'# Yellow
BBlue='\033[1;34m'  # Blue
BPurple='\033[1;35m'# Purple
BCyan='\033[1;36m'  # Cyan
BWhite='\033[1;37m' # White

# Underline
UBlack='\033[4;30m' # Black
URed='\033[4;31m'   # Red
UGreen='\033[4;32m' # Green
UYellow='\033[4;33m'# Yellow
UBlue='\033[4;34m'  # Blue
UPurple='\033[4;35m'# Purple
UCyan='\033[4;36m'  # Cyan
UWhite='\033[4;37m' # White

# Background
On_Black='\033[40m' # Black
On_Red='\033[41m'   # Red
On_Green='\033[42m' # Green
On_Yellow='\033[43m'# Yellow
On_Blue='\033[44m'  # Blue
On_Purple='\033[45m'# Purple
On_Cyan='\033[46m'  # Cyan
On_White='\033[47m' # White

# Example of usage
echo -e "${Green}This is GREEN text${Color_Off} and normal text"
echo -e "${Red}${On_White}This is Red test on White background${Color_Off}"
# option -e is mandatory, it enable interpretation of backslash escapes
printf "${Red} This is red \n"

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