DEV Community: killDevils

Bash | How to source a file from GitHub?

killDevils — Sat, 20 Jun 2020 23:39:04 +0000

When you are invoking BootStrap in HTML file, don't bother to download related files, just paste the link:

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css" integrity="sha384-9aIt2nRpC12Uk9gS9baDl411NQApFmC26EwAOH8WgZl5MYYxFfc+NcPb1dKGj7Sk" crossorigin="anonymous">

Often, for future convenience, I gather all Bash functions created by myself in a single file named funkfunc.sh, so I can source it whenever I need. But, in different projects, I still have to copy the file respectively. In most cases, the hosts are allowed to access Internet, why don't make an online version of funkfunc.sh?

Source a file from a public repo in GitHub

For example, I have a public repo: killDevils/PublicSource, there is a file named "bashKit.sh". When I view the "Raw" file of it, the Browser shows me the link: https://raw.githubusercontent.com/killDevils/PublicSource/master/bashKit.sh

Now, add a line at the top of .sh file (below shebang tag #!/bin/bash):

source <(curl -s https://raw.githubusercontent.com/killDevils/PublicSource/master/bashKit.sh)

Source a file from a PRIVATE repo in GitHub

First, please read my old post:GitHub | Download a file from a Private Repository in GitHub, get to know how to generate the link we need.

For example, The link I got is https://1234abc45678cde6543edca@raw.githubusercontent.com/killDevils/PrivateRepo/master/funkfunc.sh

Now, add a line at the top of .sh file (below shebang tag #!/bin/bash):

source <(curl -s https://1234abc45678cde6543edca@raw.githubusercontent.com/killDevils/PrivateRepo/master/funkfunc.sh)

🍻

Hope this would help! Cheers!

Bash | my personal cheat list

killDevils — Wed, 20 May 2020 06:41:12 +0000

As a Concept Director, I don't have the chance to just dive into a single language. Switching between different languages causes forgetting basic tricks. Time is consumed by searching over codes in old repositories.

The basic tricks are not worthy to write into individual posts, so list here would be a better way to record and look up.

Sure, the list is growing as long as I am coding in Bash.

Switch to root

sudo su change to root, but not environment variables.
sudo su - change to root as well as the environment variables.
sudo -i used not often

Curl

curl -s mute curl
curl -O Write output to a local file in current working directory, named like the remote file we get.

Create new file

touch /tmp/payTime an empty file called payTime created under /tmp.

Make new directory

mkdir /tmp/business made a folder called "business" under /tmp, if /tmp exists.
mkdir /tmp/company/business made a folder called "business" under /tmp/company, even /tmp and /company do not exist.

Quick go back to the working directory of current user

cd ~ or cd

Make a .sh file executable

chmod +x or chmod a+x makes it executable for everyone.
chmod u+x makes it executable for current user.
chmod g+x makes it executable for current group.
chmod o+x makes it executable for others.

Cron

crontab -l list current user's existing cron jobs.
crontab -e edit.
crontab -r remove all cron jobs.

Variable

${var} = $var. The former is really useful when the latter meets conflict with the content behind. e.g.

folder="/usr/share/"
file="password.txt"
cat $folderfile  #this would meet a big problem.
cat ${folder}file  #this is good to use.

export var=0 set a new environment variable in the current session of the current shell. Would dismiss in the next login.

awk

awk -F@ regards @ as the divider.
awk '!\name\ && \running\ {print $1}' ignore the lines contains "name", remain the lines contains running, then grab the first column.

Date and Time

date show current date and time in standard format.
date +"%Y-%m-%d %H:%M:%S" show in "2020-05-20 15:49:28" format.
date -d "+1 hour 30 minutes" +"%Y-%m-%d %H:%M:%S" show in "2020-05-20 15:49:28" format, plus 90 minutes based on current Time.
date +%s count the seconds from 1970-1-1 0:0:0 (Epoch Time).
date -d @1344127275 +"%Y-%m-%d %H:%M" count 1344127275 seconds from the Epoch Time, show in "2012-08-05 08:41:15" format (the timestamp Curiosity rover lands on Mars 🎉).

Four Operations

echo $((1+2*3-4/5)) integer only. The result is also integer.
echo 1.2+2.3*3.4-4.5/5.6 | bc -l decimal is allowed. the result is 20 decimal digits.
printf %.3f $(echo 1.2+2.3*3.4-4.5/5.6 | bc -l) to round 20 decimal digits down to 3.

Mutt

mutt -e "set realname='Kill Devils'" show a custom name in mail instead of the string before @ of your email address.

Compare numbers

Compare decimals:

if (( $(echo "50.01 >= 50.00" | bc -l) )); then
echo "50.01 is greater equal than 50.00"
fi

Compare integers:

if [[ 51 -ge 50 ]]; then
echo "51 is greater equal than 50"
fi

Background job

bash update.sh & job would run in background, but would terminate when the current session is exit.
nohup bash update.sh & nohup = no hang up. job would not be affected by current session logging out.

Redirection (stdin, stdout, stderr, screen. std = standard)

bash update.sh > output.out stdout redirects from screen to "output.out" file.
bash update.sh 2> output.err stderr redirects from screen to "output.err" file.
bash update.sh &> output.log both stdout and stderr redirect from screen to "output.log" file.
bash update.sh | tee output.log show everything on screen, redirect everything into "output.err" file as well.

Move files

mv -f force move, ignore conflicts.

Bash | How to show the external IP of your server

killDevils — Tue, 19 May 2020 00:52:38 +0000

When I was deploying a new instance on Google Cloud Platform, I often forgot the IP of it. Usually, I have to go back to Google Cloud Console and find it out in the list.

For a easier management in the future, I wanna let the instance know its IP and write it down in a txt file:

curl icanhazip.com > /usr/business/extIP

Now, each time the instance generate a daily report, it could cat /usr/business/extIP and get the IP.

Hope this helps! Cheers! 🍻

GitHub | Download a file from a Private Repository in GitHub

killDevils — Sat, 16 May 2020 02:52:51 +0000

I wrote a series of Bash scripts. They make my work on Google Cloud Platform (GCP) easier.

Since the PORT 25 for mail service is strictly blocked by GCP, and at the same time, building mail service on my own is quite complex. So, under Google's Suggestion, I decided to use SendGrid.

SendGrid utilizes a bot called GitGuardian to scan public repositories on GitHub, and would temporarily suspend your account if you accidentally pasted SendGrid's API key in it.

So, better save the API key in private repositories.

To download a file from private repository

1. You need to generate a Personal Access Tokens.

According to this GitHub help page:

In the upper-right corner of any page, click your profile photo, then click Settings.
In the left sidebar, click Developer settings.
In the left sidebar, click Personal access tokens.
Select the scopes. To use your token to access repositories from the command line, select repo.
Click Generate new token.
Give your token a descriptive name.

Let's suppose your actual token is 1234567abcdefg

2. Embed Token into the link.

Open the file in GitHub web page and click "Raw"

Copy the link of this raw file, maybe something like this:
https:// raw.githubusercontent.com/GITHUB_ACCOUNT/REPOSITORY_NAME/BRANCH_NAME/FILE_NAME.EXTENTION_NAME?token=SOME_NUMBERS_LETTERS
Reform the link as
https:// 1234567abcdefg@raw.githubusercontent.com/GITHUB_ACCOUNT/REPOSITORY_NAME/BRANCH_NAME/FILE_NAME.EXTENTION_NAME

As you see, "?token=SOME_NUMBERS_LETTERS" are removed. Insert the token you generated from GitHub + @ right after "https://"

To use the link

curl -s -O https://1234567abcdefg@raw.githubusercontent.com/GITHUB_ACCOUNT/REPOSITORY_NAME/BRANCH_NAME/FILE_NAME.EXTENTION_NAME

Hope this would help! Cheers! 🍻

Bash | Find out the usage of a certain PORT

killDevils — Sat, 09 May 2020 11:31:00 +0000

When I was trying to run acme.sh to generate SSL certification, I got an error:

[Sat May  9 18:54:10 HKT 2020] tcp port 80 is already used by 
[Sat May  9 18:54:10 HKT 2020] Please stop it first
[Sat May  9 18:54:10 HKT 2020] _on_before_issue.

I believe it is expected to show the service which is using port 80 in the first line, but nothing at all. I have to find out my self.

sudo netstat -tulpn | grep :80

I got the output:

tcp6       0      0 :::80                   :::*                    LISTEN      10541/apache2

Oh, yes, Apache2. I wanna shut it down temporally:

sudo systemctl stop apache2

Now, generate cert again:

~/.acme.sh/acme.sh --issue -d mydomain.me --standalone --keylength ec-256