switch to using go-cmd/cmd

Signed-off-by: Jeff Carr <[email protected]>

1 files changed, 184 insertions, 0 deletions

diff --git a/cmd.go b/cmd.go
new file mode 100644
index 0000000..faaa3c6
--- /dev/null
+++ b/cmd.go
@@ -0,0 +1,184 @@
+package main
+
+// this is a simplified interaction with the excellent
+// go-cmd/cmd package to work 'shell' like.
+
+// in all cases here, STDERR -> STDOUT
+// If you want the output from whatever you run
+// to be captured like it appears when you see it
+// on the command line, this is what this tries to do
+
+/*
+	if r := shell.Run([]{"ping", "-c", "3", "localhost"}); r.Error == nil {
+		if r.Exit == 0 {
+			log.Println("ran ok")
+		} else {
+			log.Println("ran")
+		}
+		// all stdout/stderr captured in r.Stdout
+	}
+*/
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/go-cmd/cmd"
+	"go.wit.com/log"
+)
+
+func Run(args []string) cmd.Status {
+	return PwdRun("", args)
+}
+
+// absolutely doesn't echo anything
+func PwdRunQuiet(pwd string, args []string) cmd.Status {
+	var arg0 string
+	var argx []string
+	// Check if the slice has at least one element (the command name)
+	if len(args) == 0 {
+		var s cmd.Status
+		s.Error = errors.New("Error: Command slice is empty.")
+		return s
+	}
+	if len(args) == 1 {
+		// Pass the first element as the command, and the rest as variadic arguments
+		arg0 = args[0]
+	} else {
+		arg0 = args[0]
+		argx = args[1:]
+	}
+
+	// Start a long-running process, capture stdout and stderr
+	findCmd := cmd.NewCmd(arg0, argx...)
+	if pwd != "" {
+		findCmd.Dir = pwd
+	}
+	statusChan := findCmd.Start() // non-blocking
+
+	ticker := time.NewTicker(2 * time.Second)
+
+	// this is interesting, maybe useful, but wierd, but neat. interesting even
+	// Print last line of stdout every 2s
+	go func() {
+		for range ticker.C {
+			status := findCmd.Status()
+			n := len(status.Stdout)
+			if n != 0 {
+				fmt.Println(status.Stdout[n-1])
+			}
+		}
+	}()
+
+	// Stop command after 1 hour
+	go func() {
+		<-time.After(1 * time.Hour)
+		findCmd.Stop()
+	}()
+
+	// Check if command is done
+	select {
+	case finalStatus := <-statusChan:
+		log.Info("finalStatus =", finalStatus.Exit, finalStatus.Error)
+		return finalStatus
+		// done
+	default:
+		// no, still running
+	}
+
+	// Block waiting for command to exit, be stopped, or be killed
+	finalStatus := <-statusChan
+	return finalStatus
+}
+
+func blah(cmd []string) {
+	r := Run(cmd)
+	log.Info("cmd =", r.Cmd)
+	log.Info("complete =", r.Complete)
+	log.Info("exit =", r.Exit)
+	log.Info("err =", r.Error)
+	log.Info("len(stdout+stderr) =", len(r.Stdout))
+}
+
+// run these to see confirm the sytem behaves as expected
+func RunTest() {
+	blah([]string{"ping", "-c", "3", "localhost"})
+	blah([]string{"exit", "0"})
+	blah([]string{"exit", "-1"})
+	blah([]string{"true"})
+	blah([]string{"false"})
+	blah([]string{"grep", "root", "/etc/", "/proc/cmdline", "/usr/bin/chmod"})
+	blah([]string{"grep", "root", "/proc/cmdline"})
+	fmt.Sprint("blahdone")
+}
+
+// sets the exec dir if it's sent
+// combines stdout and stderr
+// echo's output
+func PwdRun(pwd string, args []string) cmd.Status {
+	var save []string // combined stdout & stderr
+	var arg0 string
+	var argx []string
+	// Check if the slice has at least one element (the command name)
+	if len(args) == 0 {
+		var s cmd.Status
+		s.Error = errors.New("Error: Command slice is empty.")
+		return s
+	}
+	if len(args) == 1 {
+		// Pass the first element as the command, and the rest as variadic arguments
+		arg0 = args[0]
+	} else {
+		arg0 = args[0]
+		argx = args[1:]
+	}
+
+	// Disable output buffering, enable streaming
+	cmdOptions := cmd.Options{
+		Buffered:  false,
+		Streaming: true,
+	}
+
+	// Create Cmd with options
+	envCmd := cmd.NewCmdOptions(cmdOptions, arg0, argx...)
+	if pwd != "" {
+		envCmd.Dir = pwd
+	}
+
+	// Print STDOUT and STDERR lines streaming from Cmd
+	doneChan := make(chan struct{})
+	go func() {
+		defer close(doneChan)
+		// Done when both channels have been closed
+		// https://dave.cheney.net/2013/04/30/curious-channels
+		for envCmd.Stdout != nil || envCmd.Stderr != nil {
+			select {
+			case line, open := <-envCmd.Stdout:
+				if !open {
+					envCmd.Stdout = nil
+					continue
+				}
+				save = append(save, line)
+				fmt.Println(line)
+			case line, open := <-envCmd.Stderr:
+				if !open {
+					envCmd.Stderr = nil
+					continue
+				}
+				save = append(save, line)
+				fmt.Println(line)
+			}
+		}
+	}()
+
+	// Run and wait for Cmd to return, discard Status
+	<-envCmd.Start()
+
+	// Wait for goroutine to print everything
+	<-doneChan
+
+	s := envCmd.Status()
+	s.Stdout = save
+	return s
+}