Signal CLI

(from https://medium.com/digital-forensics-deep-learning-and-dev/simple-signal-bot-6ce841c7982e)

Download newest tar.gz release from https://github.com/AsamK/signal-cli/releases
$ cd ~
$ wget https://github.com/AsamK/signal-cli/releases/download/v0.7.2/signal-cli-0.7.2.tar.gz

Extract
$ tar -vzxf signal-cli-0.7.2.tar.gz
$ mv signal-cli-0.7.2 signal-cli

Enter
$ cd ~/signal-cli/bin

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Install Java
$ sudo apt update
$ sudo apt install default-jdk

Alternatively, if your OS only give you old java version by default like me, use:
$ sudo apt-get install dirmngr
$ echo "deb http://ppa.launchpad.net/linuxuprising/java/ubuntu bionic main" | sudo tee /etc/apt/sources.list.d/linuxuprising-java.list
$ sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 73C3DB2A
$ sudo apt update
$ sudo apt install oracle-java15-set-default

Check Java
$ java -version
\\\\\\\

Install Signal on your phone and set it up, you will need it to get confimation code.

Register
$ ./signal-cli -u +628123456789 register

Receive confirmation code from your phone, verify
$ ./signal-cli -u +628123456789 verify 123–456

Send message
$ ./signal-cli -u +628123456789 send -m "Hello hello hello,"$'\n'"World!" +628987654321
1610594445133

Receive deliver statuses, read statuses, and messages.
$ ./signal-cli -u +4915151111111 receive --json
{"envelope":{"source":"+628987654321","sourceDevice":1,"relay":null,"timestamp":1610594450743,"dataMessage":null,"syncMessage":null,"callMessage":null,"receiptMessage":{"when":1610594450743,"isDelivery":true,"isRead":false,"timestamps":[1610594445133]}}}
{"envelope":{"source":"+628987654321","sourceDevice":1,"relay":null,"timestamp":1610594451013,"dataMessage":null,"syncMessage":null,"callMessage":null,"receiptMessage":{"when":1610594451013,"isDelivery":false,"isRead":true,"timestamps":[1610594445133]}}}
{"envelope":{"source":"+628987654321","sourceDevice":1,"relay":null,"timestamp":1610594529488,"dataMessage":{"timestamp":1610594529488,"message":"World world world,\nHello!","expiresInSeconds":0,"reaction":null,"quote":null,"mentions":[],"attachments":[],"groupInfo":null},"syncMessage":null,"callMessage":null,"receiptMessage":null}}