How Do I Redirect External Process Output to Logs in Golang in Real Time?

Redirecting Process Output to Logs in Golang

When executing external processes in Golang, it can be valuable to capture and log their output promptly. While waiting for the process to finish and using CombinedOutput() allows for logging, it's impractical for long-running or unfinished processes.

Alternatively, writing to Stdout in real time is insufficient for services that don't output to a terminal. One solution is to leverage pipes for efficient output redirection.

Utilizing Pipes for Redirection

A pipe creates a connection between processes, enabling data transfer. To redirect process output to logs, follow these steps:

1. Pipe Creation: Create a pipe for reading the process's Stdout using StdoutPipe().
2. Process Execution: Start the process with the established pipe.
3. Output Reading: Read the Stdout pipe's output line by line using a buffered scanner.
4. Logging: Write each line to the desired log by utilizing log.Printf().

Adding a handler for Stderr can be achieved by creating a goroutine for simultaneous handling of both output channels.

Example Implementation:

Consider the following code snippet using pipes for output redirection:

stdout, err := cmd.StdoutPipe()
if err != nil {
    return 0, err
}

if err := cmd.Start(); err != nil {
    return 0, err
}

in := bufio.NewScanner(stdout)

for in.Scan() {
    log.Printf(in.Text())
}
if err := in.Err(); err != nil {
    log.Printf("error: %s", err)
}

By employing this approach, you can effectively capture and log the output of external processes in a timely manner, ensuring valuable information is available for debugging and analysis.

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