How to use Docker compose in c program?

Question

I want to isolate my development environment to create a project in C. But I don't know how to use Docker with C. I'm getting confused about running the program and I would like someone to help me. Take for example a "hello world" with an input. basic as a program. How can I make a docker compose and how to run it. And still with live-reload?

hello.c:

#include <stdio.h>
int main() {
  int numero;

  // Pede um número ao usuário
  printf("Digite um número: ");
  scanf("%d", &numero);

  // Exibe o número digitado na tela
  printf("O número digitado foi: %d\n", numero);

  return 0;
}

Dockerfile:

FROM gcc:latest

COPY . /app

WORKDIR /app/

RUN gcc -o app hello.c

CMD [“./app"]

Answer 1

It's good practice (although not required) to treat containers as immutable.

In this scenario, whenever your code changes, you rebuild and create a uniquely new image.

There are various ways to work with mutable containers:

1. Use a container interactively e.g. Bash to edit the code, compile it etc.
2. Mount host files into a container (possibly in combination with #1)
3. Copy files in|out of a running container

Some combination of these approaches may serve your needs but be careful to ensure you do so correctly so that you persist changes to files in the container:

You can create an interactive shell on a container from the gcc:latest image and mount files e.g. your source code into a folder on it:

WORK="/app"

docker run \
--interactive --tty --rm \
--volume=${PWD}/hello.c:${WORK}/hello.c \
--workdir=${WORK} \
gcc:latest

This will mount ${PWD}/hello.c into the container's /app folder and make this the working directory.

When you run the docker command, you should see:

# ls
hello.c

You can then:

# gcc -o hello hello.c
# ls 
hello hello.c
# ./hello
Digite um número: 55
O número digitado foi: 55

Any changes you make to hello.c (only) will be reflected in the copy on your host.