Make /v flag optional

[MarkTiedemann]

tasklist seems to be round about 1 second slower when used with the verbose flag. Therefore, I propose making the /v flag optional.

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Using timeit from the Windows Server 2003 Resource Kit Tools, I got the following outputs:

timeit tasklist:

Version Number:   Windows NT 6.2 (Build 9200)
Exit Time:        5:05 pm, Friday, March 3 2017
Elapsed Time:     0:00:00.114
Process Time:     0:00:00.015
System Calls:     56499
Context Switches: 23459
Page Faults:      6867
Bytes Read:       1708
Bytes Written:    117698
Bytes Other:      1061894

timeit tasklist /v:

Version Number:   Windows NT 6.2 (Build 9200)
Exit Time:        5:05 pm, Friday, March 3 2017
Elapsed Time:     0:00:01.359
Process Time:     0:00:00.062
System Calls:     244191
Context Switches: 65230
Page Faults:      43840
Bytes Read:       19524
Bytes Written:    648250
Bytes Other:      6542373

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Hope I'm gonna be able to submit a PR soon. :)

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EDIT: Just noticed there's already a closed issue regarding tasklist being slow: #4. It was closed as a wontfix. Making the /v flag optional, however, would be that missing fix.

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Another question in this regard would be: Should the verbose option be true or false by default? I'm leaning towards false considering the performance impact.

[sindresorhus]

What is the difference between verbose and non-verbose output?

[MarkTiedemann]

Normal output is:

• imageName
• pid
• sessionName
• sessionNumber
• memUsage

Verbose output is (normal output plus):

• status
• username
• cpuTime
• windowTitle

Making the /v flag optional would be a breaking change, of course.

PS: Just writing a PR. :)

PPS: Love your work.

[MarkTiedemann]

Another thought: How about adding a stream or even emitter interface? This would be nice for running the verbose option on slow systems, especially if you're not interested in all tasks anyway.

[sindresorhus]

How about adding a stream or even emitter interface?

Does tasklist.exe actually stream the output though?

[MarkTiedemann]

Yeah, tasklist.exe outputs in chunks.

For a streaming implementation, I'm thinking about something along the lines of this ...

const spawn = require('child_process').spawn
const Transform = require('stream').Transform
const csv = require('csv')

module.exports = () => 
  spawn('tasklist.exe', ['/fo', 'csv'])
  .stdout
  .pipe(csv.parse({
    columns: [ 'imageName', 'pid', 'sessionName', 'sessionNumber', 'memUsage' ],
    from: 2 // skip header record
  }))
  .pipe(new Transform({
    objectMode: true,
    transform(task, encoding, callback) {
      callback(null, Object.assign(task, {
        pid: Number(task.pid),
        sessionNumber: Number(task.sessionNumber),
        memUsage: 1024 * Number(task.memUsage.replace(/[^\d]/g, ''))
      }))
    }
  }))

... which could be used like this ...

const tasklist = require('tasklist')

tasklist()
  .on('data', console.log)
  /* => { imageName: 'tasklist.exe',
          pid: 9620,
          sessionName: 'Console',
          sessionNumber: 3,
          memUsage: 864420 } */

Should this be part of this module, though? Or would it be better to put it in a new one, for example, tasklist-stream?

[MarkTiedemann]

If anyone reading this issue is interested in a streaming interface, check out tasklist-stream. :)