Useful things found while using Linux

Here I note down all things related to Linux which I find interesting. Those can be just short notes or tips and tricks to future reference.

Makefile

Makefile is a wonderful utility application that allows to define rules which are then run in the order of their definition.

target ... : prerequisites ...
        command
        ...
        ...

Mostly Makefile makes it easier to execute two or more commands in a single execution or abbreviate a lengthy command.

For example, docker-compose up -d can be abbreviated or aliased as make up.

Or, make pg-src runs

curl -i -X POST -H "Accept:application/json" -H "Content-Type:application/json" localhost:8083/connectors/ -d '@./connectors/pg-src-connector.json'

Or, make tsetup which expands to tsetup: tup tc ci runs two or more make commands sequentially as those targets mentioned as prerequistes.

tup:
    docker-compose -f docker-compose-test.yml up -d
    @echo -n "sleeping for 30s to launch all containers..."
    @sleep 30

test-connections:
    . ./tests/setup-connections.sh
    @echo -n "sleeping for 10s to get ready for testing..."
    @sleep 10

ci:
    docker exec test_suite pytest -p no:warnings -v

The @ flag infront of an echo command or any Linux command, suppresses its output

Usually each line inside a target gets displayed before executing. Sometimes it is unnecessary. For example, @echo -n "sleeping for 10s to get ready for testing..." won’t display echo -n "sleeping for 10s to get ready for testing..." but rather just sleeping for 30s to launch all containers....

@ flag in front of sleep command suppresses sleep 30 being displayed as we already written a longer sentence previously.