How can I pass environment variables to an external command using exec.Command in Go?

Passing Environment Variables to exec.Command

When invoking external commands via the exec.Command function, it is often necessary to pass environment variables along with the command. This can be crucial for configuring and tailoring the behavior of the invoked command.

Consider a case where you want to pass an environment variable named MY_VAR with a specific value to the ansible-playbook command. To achieve this, you can utilize the Env field of the Cmd struct returned by exec.Command. However, it's crucial to be aware that setting Env directly overrides all existing environment variables.

To avoid this, you can preserve the existing environment and append the desired variable with its value. This can be accomplished as follows:

import (
    "os"
    "os/exec"
)

func main() {
    cmd := exec.Command("ansible-playbook", args...)
    cmd.Env = os.Environ()                          // Preserve existing environment
    cmd.Env = append(cmd.Env, "MY_VAR=some_value") // Append desired variable
    // Execute the command as usual
}

By adopting this approach, you can selectively override specific environment variables while preserving all others. This technique is particularly useful in scenarios where multiple invocations of external commands require different environmental configurations.

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