Question 274433 in Docker Question posted in
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Running the program in Docker with command line arguments

I need to write a program that accepts and outputs a command line argument. It is necessary to assemble it and run it in a container. Here’s what I have:

main.go:

package main

import (
    "fmt"
    "os"
)

func main() {
    if len(os.Args) > 2 {
        fmt.Println("arg: ", os.Args[1])
    } else {
        fmt.Println("no args")
    }
}

Dockerfile:

FROM golang:latest

COPY . /tmp

WORKDIR /tmp

RUN go build -o app main.go

CMD [ "./app" ]

build:

sudo docker build -t test .

run:

sudo docker run test arg1

When I start, I get an error:

docker: Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: exec: "arg1": executable file not found in $PATH: unknown.
ERRO[0002] error waiting for container:

How to fix it?

Tags:

2

Answers


  1. 0

    You can use environment variables to pass the arguments given at container startup to the entrypoint of your software.

    Dockerfile:

    # ...
ENTRYPOINT [ "./app", $my_args ]

    Commands:

    sudo docker build -t test . 
sudo docker run -e my_args="arg1" test

    You can also use a combination of ARG and ENV to create a default value that can be edited. Response from Alexander Mills on another thread.

    Edit: I didn’t deduct from your question whether this program will be run as part of a larger process, but depending on whether you need to redirect STDOUT of the program called in the container (chain to other programs) use or omit the -t flag of the docker run command.

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  2. 0

    You have two choices:

    1. You can invoke your container like this: sudo docker run test ./app arg1 arg2 arg3

    2. change the last line of your Dockerfile to say this: ENTRYPOINT [ "./app" ]

    There are subtle differences between ENTRYPOINT and CMD: https://docs.docker.com/engine/reference/run/#cmd-default-command-or-options

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