os/exec: does not report error for exec.Command when the file does not exist

[dongweigogo]

go 1.8.4

In running an exec.Command against files, Go does not report any error when the file does not exist. A simple example as below:

``

    cmd:=exec.Command("grep", "abc", "test.txt")     //actually, "test.txt" does not exist
    so,err1:=cmd.StdoutPipe()
    fmt.Println(err1)
    cmd.Start()
    buf,err2:=ioutil.ReadAll(so)
    fmt.Println(string(buf), err2)
    cmd.Wait()

``
Both err1 and err2 are nil, and no error is shown. It looks like the program runs successfully, but actually not.

[davecheney]

Go does not report any error because you are ignoring the error from cmd.Start() and `cmd.Wait().

I am going to close this issue as this appears to be a request for support, not a bug report. We only use our bug tracker for tracking bugs and tracking proposals going through the Proposal Process.

Please see https://golang.org/wiki/Questions for good places to ask questions.

[dongweigogo]

@davecheney , well, the cmd.Start() still does not report any error, but cmd.Wait() does. It looks weird, why do we just report it at the begining, in Start but not in Wait?

[as]

If cmd.Start doesn't report an error when the file doesn't exist, are there any conditions in which is reports an error?

[bradfitz]

@as, yes, Start returns an error if the process fails to start. Wait returns an error if the process fails to finish. It doesn't know that test.txt is a filename vs any other arbitrary string. It's just an argument to grep, for grep to deal with.

Let's move discussion to golang-nuts.

[as]

@bradfitz

My bad, the title of the issue made me think that file was referring to the grep binary itself.