golang-examples/shell/run.go

package shell

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strings"
	"time"

	"github.com/svent/go-nbreader"

	"go.wit.com/log"
)

func (cmd *OldShell) Run(cmdline string) string {
	cmd.InitProcess(cmdline)
	if cmd.Error != nil {
		return ""
	}
	cmd.Exec(cmdline)
	return Chomp(cmd.Buffer)
}

func (cmd *OldShell) InitProcess(cmdline string) {
	log.Log(RUN, "shell.InitProcess() START "+cmdline)

	cmd.Cmdline = Chomp(cmdline) // this is like 'chomp' in perl
	cmdArgs := strings.Fields(cmd.Cmdline)
	if len(cmdArgs) == 0 {
		cmd.Error = fmt.Errorf("cmdline == ''")
		cmd.Done = true
		return
	}
	if cmdArgs[0] == "cd" {
		if len(cmdArgs) > 1 {
			log.Log(RUN, "os.Chdir()", cmd)
			os.Chdir(cmdArgs[1])
		}
		handleError(nil, 0)
		cmd.Done = true
		return
	}

	cmd.Process = exec.Command(cmdArgs[0], cmdArgs[1:len(cmdArgs)]...)
}

func (cmd *OldShell) FileCreate(out string) {
	var newfile File

	var iof io.ReadCloser
	if out == "STDOUT" {
		iof, _ = cmd.Process.StdoutPipe()
	} else {
		iof, _ = cmd.Process.StderrPipe()
	}

	newfile.Fio = iof
	newfile.Fbufio = bufio.NewReader(iof)
	// newfile.Fnbreader = nbreader.NewNBReader(newfile.Fbufio, 1024)

	if out == "STDOUT" {
		cmd.STDOUT = &newfile
	} else {
		cmd.STDERR = &newfile
	}
}

// NOTE: this might cause problems:
// always remove the newlines at the end ?
func (cmd *OldShell) Exec(cmdline string) {
	log.Log(RUN, "shell.Run() START "+cmdline)

	cmd.InitProcess(cmdline)
	if cmd.Error != nil {
		return
	}

	cmd.FileCreate("STDOUT")
	cmd.FileCreate("STDERR")

	cmd.Process.Start()

	// TODO; 'goroutine' both of these
	// and make your own wait that will make sure
	// the process is then done and run process.Wait()
	go cmd.Capture(cmd.STDERR)
	cmd.Capture(cmd.STDOUT)

	// wait until the process exists
	// https://golang.org/pkg/os/exec/#Cmd.Wait
	// What should happen here, before calling Wait()
	// is checks to make sure the READERS() on STDOUT and STDERR are done
	err := cmd.Process.Wait()

	// time.Sleep(2 * time.Second) // putting this here doesn't help STDOUT flush()

	if err != nil {
		cmd.Fail = true
		cmd.Error = err
		log.Log(RUN, "process.Wait() END err =", err.Error())
	} else {
		log.Log(RUN, "process.Wait() END")
	}
	return
}

// nonblocking read until file errors
func (cmd *OldShell) Capture(f *File) {
	log.Log(RUN, "nbrREADER() START")

	if cmd.Buffer == nil {
		cmd.Buffer = new(bytes.Buffer)
	}
	if cmd.Buffer == nil {
		f.Dead = false
		cmd.Error = fmt.Errorf("could not make buffer")
		log.Error(cmd.Error, "f.Buffer == nil")
		log.Error(cmd.Error, "SHOULD DIE HERE")
		cmd.Done = true
	}

	f.Dead = false

	// loop that keeps trying to read from f
	for f.Dead == false {
		time.Sleep(time.Duration(msecDelay) * time.Millisecond) // only check the buffer 500 times a second

		// set to false so it keeps retrying reads
		f.Empty = false

		// tight loop that reads 1024 bytes at a time until buffer is empty
		// 1024 is set in f.BufferSize
		for f.Empty == false {
			f.Empty = cmd.ReadToBuffer(f)
		}
	}
}

// returns true  if filehandle buffer is empty
func (cmd *OldShell) ReadToBuffer(f *File) bool {
	log.Log(RUN, "ReadToBuffer() START")
	// nbr := f.Fnbreader
	// newfile.Fnbreader = nbreader.NewNBReader(newfile.Fbufio, 1024)
	nbr := nbreader.NewNBReader(f.Fbufio, 1024)
	oneByte := make([]byte, 1024)
	if nbr == nil {
		// log.Debugln("ReadToBuffer() ERROR nbr is nil")
		f.Dead = true
		return true
	}
	count, err := nbr.Read(oneByte)
	f.TotalCount += count

	if err != nil {
		// log.Debugln("ReadToBuffer() file has closed with", err)
		// log.Debugln("ReadToBuffer() count = ", count, "err = ", err)
		f.Dead = true
		return true
	}
	if count == 0 {
		// log.Debugln("ReadToBuffer() START count == 0 return true")
		return true
	}
	// log.Debugln("ReadToBuffer() count = ", count)
	// tmp := Chomp(oneByte)
	// log.Debugln("ReadToBuffer() tmp = ", tmp)
	io.WriteString(cmd.Buffer, strings.Trim(string(oneByte), "\x00"))
	return false
}

// pass in two file handles (1 read, 1 write)
func nonBlockingReader(buffReader *bufio.Reader, writeFileHandle *os.File, stdout *bufio.Writer) {
	// newreader := bufio.NewReader(readFileHandle)

	// create a nonblocking GO reader
	nbr := nbreader.NewNBReader(buffReader, 1024)

	for {
		// defer buffReader.Close()
		// defer writeFileHandle.Flush()
		defer writeFileHandle.Close()
		totalCount := 0
		for {
			oneByte := make([]byte, 1024)
			count, err := nbr.Read(oneByte)
			if err != nil {
				log.Log(INFO, "count, err =", count, err)
				handleError(err, -1)
				return
			}
			totalCount += count
			if count == 0 {
				time.Sleep(time.Duration(msecDelay) * time.Millisecond) // without this delay this will peg the CPU
				if totalCount != 0 {
					log.Log(INFO, "STDERR: totalCount = ", totalCount)
					totalCount = 0
				}
			} else {
				log.Log(INFO, "STDERR: count = ", count)
				writeFileHandle.Write(oneByte[0:count])
				if quiet == false {
					stdout.Write(oneByte[0:count])
					stdout.Flush()
				}
			}
		}
	}
}