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
Related
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.
I am trying to get the duration of a video using ffprobe and exec.Command but I keep getting an error. However, stdout and stderr are both empty so I don't know what the problem is.
func getVideoLength(filename string) float64 {
cmd := exec.Command("ffprobe", "-i", filename, "-show_entries", "format=duration", "-v", "quiet", "-of", "csv=\"p=0\"")
fmt.Println("ffprobe", "-i", filename, "-show_entries", "format=duration", "-v", "quiet", "-of", "csv=\"p=0\"")
var out bytes.Buffer
var stderr bytes.Buffer
cmd.Stdout = &out
cmd.Stderr = &stderr
err := cmd.Run()
if err != nil {
fmt.Println("out: " + out.String())
fmt.Println("stderr: " + stderr.String())
log.Fatal(err)
}
length, err := strconv.ParseFloat(out.String(), 64)
if err != nil {
log.Fatal(err)
}
return length
}
Here is the output I get:
ffprobe -i amelie.mp4 -show_entries format=duration -v quiet -of csv="p=0"
out:
stderr:
2019/02/18 21:04:39 exit status 1
not very helpful.
Any ideas?. Thanks.
The reason you aren't getting any clues is that you have set the command to not say anything. From the ffprobe docs
-loglevel [flags+]loglevel | -v [flags+]loglevel Set logging level and flags used by the library.
....
loglevel is a string or a number containing one of the following
values:
‘quiet, -8’ Show nothing at all; be silent.
I am using gnupg to encrypt files with the following command:
gpg --encrypt --sign --armor -r person#email.com name_of_file
This command works fine in shell. But it fails in go program with following error :
gpg: cannot open '/dev/tty': Device not configured
Here is the Code:
func main() {
var stdout, stderr bytes.Buffer
cmd := exec.Command("/bin/sh", "-c", `gpg --encrypt --sign --armor -r person#email.com file_name.csv`)
cmd.Stdout = &stdout
cmd.Stderr = &stderr
err := cmd.Run()
if err != nil {
log.Println(err)
}
out := stdout.String() + stderr.String()
fmt.Println(out)
}
Why am I getting this error and how can I fix it?