CODEWITHSUNDEEP
go
gextra
gextra

Reputation: 8885

unable to see command arguments at OS level issued from exec.Command

My routine is supposed to spin 10 child processes from the same go executable binary (os.Args[0]), adding some command line arguments that are valid. All processes should live for a number of seconds, which is specified in one of the arguments.

func spinChildProcesses() {
    cmdParts := make([]string, 4)
    cmdParts[0] = "-c"
    cmdParts[1] = os.Args[0]
    cmdParts[2] = "--duration"
    cmdParts[3] = "10000"
    for i := 0; i < 10; i++ {
        proc := exec.Command("bash", cmdParts...)
        go proc.Start()
    }
}

func main() {
    # not showing code that parses duration arg
    # create 10 child subprocesses
    go spinChildProcesses()
    // set a duration to the process and terminate
    time.Sleep(time.Second * time.Duration(duration))
    fmt.Println(" - process terminating normaly")
}

When the above is run, looking at OS level I can see the arguments are not carried out. Only the root process has the arguments which I typed:

ps -ef | grep my-test-pr
root      3806 14446  0 15:23 pts/1    00:00:00 ./my-test-pr --duration 10000
root      3810  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3811  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3813  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3814  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3818  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3823  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3824  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3829  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3836  3806  0 15:23 pts/1    00:00:00 ./my-test-pr
root      3840  3806  0 15:23 pts/1    00:00:00 ./my-test-pr

Any idea why and how to ensure the arguments are passed to the children processes ?

Upvotes: 0

Views: 114

Answers (1)

Mr_Pink
Mr_Pink

Reputation: 109347

The -c bash flag takes a single string argument to interpret. Since the argument to -c is only the string os.Args[0], that is all bash is executing, and the rest of the args are being ignored.

To provide the arguments to your binary to be executed by bash -c, join them into a single string:

var args []string
args = append(args, os.Args[0])
args = append(args, "--duration")
args = append(args, "10000")
for i := 0; i < 10; i++ {
    proc := exec.Command("/bin/bash", "-c", stringsJoin(args, " "))
    go proc.Start()
}

Or simply exec your binary directly without the extra shell.

Upvotes: 3

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