Trying to run terminal commands in Go using exec to get docker network usage but unable to. The following link shows how to get docker container's network usage using terminal and it works fine in terminal but not using Go. https://docs.docker.com/config/containers/runmetrics/
I get exit code 1, 2, 125, etc. with different combinations.
stdin, err := cmd.StdinPipe()
if err != nil {
log.Fatal(err)
}
defer stdin.Close()
io.WriteString(stdin, "CID="+CID) // container ID
io.WriteString(stdin,"TASKS=/sys/fs/cgroup/devices/docker/$CID*/tasks")
io.WriteString(stdin, "PID=$(head -n 1 $TASKS)")
io.WriteString(stdin, "mkdir -p /var/run/netns")
io.WriteString(stdin, "ln -sf /proc/$PID/ns/net /var/run/netns/$CID")
io.WriteString(stdin, "ip netns exec $CID netstat -i")
out, err := cmd.CombinedOutput()
if err != nil {
log.Fatal(err)
}
fmt.Printf("%s\n", out)
Expected output:
Kernel Interface table
Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0 1450 1228323 0 0 0 1761314 0 0 0 BMRU
If someone looks for the same in the future, here's a working solution
cmd := exec.Command("/bin/sh", "-c", "CID="+CID+" ; TASKS=/sys/fs/cgroup/devices/docker/$CID*/tasks ; PID=$(head -n 1 $TASKS); mkdir -p /var/run/netns ; ln -sf /proc/$PID/ns/net /var/run/netns/$CID ; ip netns exec $CID netstat -i")
out, err := cmd.CombinedOutput()
if err != nil {
fmt.Println(err)
}
fmt.Printf("%s\n", out)
Related
cmdstr := "ssh -i ....... blah blah blah" ssh to an ip and run rpm command to install rpm
cmd := exec.Command("/bin/bash", "-c", cmdstr)
var out bytes.Buffer
cmd.Stdout = &out
err := cmd.Run()
if err != nil {
fmt.Println(out.String())
}
out.String() does not print anything
if I have ping command without /bin/bash it prints the out. Anyone knows why ?
cmd.Stdout captures the output of a successful command execution
cmd.Stderr captures the command output if an error occurs during execution
You could try the cmd.Output() variant and capture execution errors from Stderr using
cmdstr := "ssh -i ....... blah blah blah" // ssh to an ip and run rpm command to install rpm
cmd := exec.Command("/bin/bash", "-c", cmdstr)
var errb bytes.Buffer
cmd.Stderr = &errb
output, err := cmd.Output()
if err != nil {
fmt.Printf("error: %s", errb.String()) // capture any error output
}
fmt.Println(string(output)) // when successful
I have a shell command
set -a source /etc/environment; set +a
I want to run this command to refresh my env file
the code I tried to do
cmd, err := exec.Command("bash", "set -a source /etc/environment; set +a").Output()
fmt.Println("cmd=================>", cmd)
if err != nil {
fmt.Println(err)
}
it gave me exit status 127
try this
cmd, err := exec.Command("bash","-c", "set -a source /etc/environment; set +a").Output()
fmt.Println("cmd=================>", cmd)
if err != nil {
fmt.Println(err)
}
I am attempting to run the following code in Go. I have tried both of the following ways:
out, err := exec.Command("sh", "-c", "tcpdump -i ens0 host 192.168.1.100 -F ./testfile").Output()
fmt.Println(string(out)) // Prints nothing
fmt.Println(err) // exit status 1
I have also tried replacing sh with /bin/bash.
I have also tried the following, with and without sh as the first argument:
out, err := exec.Command("tcpdump", "-i", "ens0", "host", "192.168.1.100", "-F", "./testfile").Output()
fmt.Println(string(out)) // Prints nothing
fmt.Println(err) // exit status 1
None of this is working. Can someone see what I am doing wrong? I have also tried this go package "github.com/kami-zh/go-capturer" to read stderr and again it prints nothing.
Normally I have to use sudo to execute tcpdump from shell, so I build the go binary and execute it as root user.
Something like this should work, i am not sure if there is any specific command like -F available in tcp dump,
If you want to capture plain output of the tcp dump , you can direct the output to file using > file . The -w option is for wireshark/tcpdump format , to read and display
cmd := exec.Command("sh", "-c", "sudo tcpdump -i <eth> host <ip> -w ./testfile")
err := cmd.Run()
if err != nil {
fmt.Println(err)
}
Thanks, #torek, the -c option can be used with tcpdump to exit after capturing n packets
cmd := exec.Command("sh", "-c", "sudo tcpdump -i ens33 -c 100 host localhost -w ./testfile")
err := cmd.Run()
if err != nil {
fmt.Println(err)
}
The other way is to use cmd.Start
cmd := exec.Command("sh", "-c", "sudo tcpdump -i ens33 -c 100 host localhost -w ./testfile")
err := cmd.Start()
if err != nil {
log.Fatal(err)
}
log.Printf("Waiting for command to finish...")
err = cmd.Wait()
log.Printf("Command finished with error: %v", err)
The tcpdump command continue to run infinitely if you use cmd.run without -c option with tcpdump cmd.So you can't see if you put print statement after cmd.Run() call, the reason being the exec.Command failed is, it just work the same way on how it works from the cli, so if you need sodo in front for it , you should put it in command as well or run it from the root user.
I am trying to execute set of commands in Go using exec.Command(). Where I am trying to detach Gluster peer using Docker Exec.
fmt.Println("About to execute gluster peer detach")
SystemdockerCommand := exec.Command("sh", "-c", "docker exec ", "9aa1124", " gluster peer detach ", "192.168.1.1", " force")
var out bytes.Buffer
var stderr bytes.Buffer
SystemdockerCommand.Stdout = &out
SystemdockerCommand.Stderr = &stderr
err := SystemdockerCommand.Run()
if err != nil {
fmt.Println(fmt.Sprint(err) + ": " + stderr.String())
}
fmt.Println("System Docker exec : " + out.String())
I was expecting a result as "no peer to detatch". But got
exit status 1: "docker exec" requires at least 2 arguments.
Since you have used sh -c, the next parameter should be the full command or commands:
SystemdockerCommand := exec.Command("sh", "-c", "docker exec 9aa1124 gluster peer detach 192.168.1.1 force")
More generally, as in here:
cmd := exec.Command("/bin/sh", "-c", "command1 param1; command2 param2; command3; ...")
err := cmd.Run()
See this example:
sh := os.Getenv("SHELL") //fetch default shell
//execute the needed command with `-c` flag
cmd := exec.Command(sh, "-c ", `docker exec 9aa1124 ...`)
Or this one, putting your commands in a string first:
cmd := "cat /proc/cpuinfo | egrep '^model name' | uniq | awk '{print substr($0, index($0,$4))}'"
out, err := exec.Command("bash","-c",cmd).Output()
if err != nil {
return fmt.Sprintf("Failed to execute command: %s", cmd)
}
multipass exec kube-node-one -- bash -c "ls && ls -a"
Is there any way we can execute a multiple commands in exec.Command
No.
virt-install \
-n "NAME" \
-r 1024 \
--import \
--disk path="1703_Disk.img" \
--accelerate \
--network network=default \
--connect=qemu:///system \
--vnc \
-v
Can someone explain me how to execute this in Go.
The os/exec package is what you're looking for:
cmdName := "virt-install"
args := []string{
"-n", "NAME",
"-r", "1024",
"--import",
"--disk", "path=1703_Disk.img"
"--accelerate",
"--network", "network=default",
"--connect=qemu:///system",
"-vnc",
"-v",
}
cmd := exec.Command(cmdName, args...)
if err := cmd.Start(); err != nil {
log.Fatal(err)
}
if err := cmd.Wait(); err != nil {
log.Fatal(err)
}
There is a Go API for libvirt, either the one at https://gitlab.com/libvirt/libvirt-go-module or the https://github.com/digitalocean/go-libvirt one. For some tasks, it makes more sense to use that, instead of running libvirt commands as a subprocess.
The virt-install case probably makes most sense as a subprocess, however.