I have a script I want to run on remote via ssh. It checks if there is a process running and should try to kill it, if it exists. Now, my code looks like this:
ssh my_prod_env << ENDSSH
...
pid=$(pgrep -f "node my_app.js")
echo $pid
# kill process with $pid
...
exit
ENDSSH
The problem lies here: I cannot capture output of pgrep command in variable. I tried with $(), backticks, pipe then read and maybe other approaches, but all without success.
I would like to do it all in one ssh session.
Now I am thinking the output of command goes to the output stream I cannot access in my script. I might be wrong, though.
Either way, help will be appreciated.
Ok, after you provided in comments more info what you want, I believe this is the correct answer to your question:
ssh my_prod_env -t 'pgrep -f "node my_app.js"'
This will call the command and leave you logged on the server
This is what fixes the thing - "escaping" the ENDSSH tag.
ssh my_prod_env << /ENDSSH
...
# capture output of remote commands in remote variables
...
ENDSSH
Problem was that my vars were local and I was trying to capture output of remote commands in them.
This question/answer helped me realize what is going on: How to assign local variable with a remote command result in bash script?
So, my question could be marked as duplicate or something similar, I guess.
Related
I want to log into server based on user's choice so I wrote bash script. I am totally newbie - it is my first bash script:
#!/bin/bash
echo -e "Where to log?\n 1. Server A\n 2. Server B"
read to_log
if [ $to_log -eq 1 ] ; then
echo `ssh user#ip -p 33`
fi
After executing this script I am able to put a password but after nothing happens.
If someone could help me solve this problem, I would be grateful.
Thank you.
The problem with this script is the contents of the if statement. Replace:
echo `ssh user#ip -p 33`
with
ssh user#ip
and you should be good. Here is why:
Firstly, the use of back ticks is called "command substitution". Back ticks have been deprecated in favor of $().
Command substitution tells the shell to create a sub-shell, execute the enclosed command, and capture the output for assignment/use elsewhere in the script. For example:
name=$(whoami)
will run the command whoami, and assign the output to the variable name.
the enclosed command has to run to completion before the assignment can take place, and during that time the shell is capturing the output, so nothing will display on the screen.
In your script, the echo command will not display anything until the ssh command has completed (i.e. the sub-shell has exited), which never happens because the user does not know what is happening.
You have no need to capture the output of the ssh command, so there is no need to use command substitution. Just run the command as you would any other command in the script.
I have a series of bash commands, some with interactive prompts, that I need run on a remote machine. I have to have them called in a certain order for different scenarios, so I've been trying to make a bash script to automate the process for me. However, it seems like every way to start an ssh session with a bash script results in the the redirection of stdin to whatever string or file was used to initiate the script in the first place.
Is there a way I can specify that a certain script be executed on a remote machine, but also forward stdin through ssh to the local machine to enable the user to interact with any prompts?
Here's a list of requirements I have to clarify what I'm trying to do.
Run a script on a remote machine.
Somewhere in the middle of that remote script be command that will prompt for input. Example: git commit will bring up vim.
If that command is git commit and it brings up vim, the user should be able to interact with vim as if it was running locally on their machine.
If that command prompts for a [y/n] response, the user should be able to input their answer.
After the user enters the necessary information—by quitting vim or pressing return on a prompt—the script should continue to run like normal.
My script will then terminate the ssh session. The end product is that commands were executed for the user without them needing to be aware that it was through a remote connection.
I've been testing various different methods with the following script that I want run on the remote machine.
#!/bin/bash
echo hello
vim
echo goodbye
exit
It's crucial that the user be able to use vim, and then, when the user finishes, "goodbye" should be printed to the screen and the remote session should be terminated.
I've tried uploading a temporary script to the remote machine and then running ssh user#host bash /tmp/myScript, but that seems to also take over stdin completely, rendering it impossible to let the user respond to prompts for user input. I've tried adding the -t and -T options (I'm not sure if they're different), but I still get the same result.
One commenter mentioned using expect, spawn, and interact, but I'm not sure how to use those tools together to get my desired behavior. It seems like interact will result in the user gaining control over stdin, but then there's no way to have it relinquished once the user quits vim in order to let my script continue execution.
Is my desired behavior even possible?
Ok, I think I've found my problem. I was creating a wrapper script for ssh that looked like this:
#!/bin/bash
tempScript="/tmp/myScript"
remote=user#host
commands=$(</dev/stdin)
cat <(echo "$commands") | ssh $remote "cat > $tempScript && chmod +x $tempScript" &&
ssh -t $remote $tempScript
errorCode=$?
ssh $remote << RM
if [[ -f $tempScript ]]; then
rm $tmpScript
fi
RM
exit $errorCode
It was there that I was redirecting stdin, not ssh. I should have mentioned this when I formulated my question. I read through that script over and over again, but I guess I just overlooked that one line. Removing that line totally fixed my problem.
Just to clarify, changing my script to the following totally fixed my problem.
#!/bin/bash
tempScript="/tmp/myScript"
remote=user#host
commands="$#"
cat <(echo "$commands") | ssh $remote "cat > $tempScript && chmod +x $tempScript" &&
ssh -t $remote $tempScript
errorCode=$?
ssh $remote << RM
if [[ -f $tempScript ]]; then
rm $tmpScript
fi
RM
exit $errorCode
Once I changed my wrapper script, my test script described in the question worked! I was able to print "hello" to the screen, vim appeared and I was able to use it like normal, and then once I quit vim "goodbye" was printed and the ssh client closed.
The commenters to the question were pointing me in the right direction the whole time. I'm sorry I only told part of my story.
I've searched for solutions to this problem several times in the past, however never finding a fully satisfactory one. Piping into ssh looses your interactivity. Two connects (scp/ssh) is slower, and your temporary file might be left lying around. And the whole script on the command line often ends up in escaping hell.
Recently I encountered that the command line buffer size is usually quite large (getconf ARG_MAX > 2MB where I looked). And this got me thinking about how I could use this and mitigate the escaping issue.
The result is:
ssh -t <host> /bin/bash "<(echo "$(cat my_script | base64 | tr -d "\n")" | base64 --decode)" <arg1> ...
or using a here document and cat:
ssh -t <host> /bin/bash $'<(cat<<_ | base64 --decode\n'$(cat my_script | base64)$'\n_\n)' <arg1> ...
I've expanded on this idea to produce a fully working BASH example script sshx that can run arbitrary scripts (not just BASH), where arguments can be local input files too, over ssh. See here.
In one of my bash script I want to read and use the variable value from other script which is on remote machine.
How should I go ahead to resolve this. Any related info would be helpful.
Thanks in advance!
How about this (which is code I cannot currently test myself):
text=$(ssh yourname#yourmachine 'grep uploadRate= /root/yourscript')
It assumes that the value of the variable is contained in one line. The variable text now contains you variable assignment, presumably something like
uploadRate=1MB/s
There are several ways to convert the text/code into a real variable assignment in your current script, like evaluating the string or using grep. I would recommend
uploadRate=${text#*=}
to just remove the part up and including the =.
Edit: One more caveat to mention is that this only works if the original assignment does not contain variable references itself like in
uploadRate=1000*${kB}/s
ssh user#machine 'command'
will print the standard output of the remote command.
I would tell two ways at least:
1) You can simply redirect output to a file from remote server to your system with scp command...It would work for you.Then your script on your machine should read that file as an argument...
script on your machine:
read -t 50 -p "Waiting for argumet: " $1
It waits for output from remote machine,
Then you can
sshpass -p<password> scp user#host:/Path/to/file /path/to/script/
What you need to do:
You should tell the script from your machine, that the output from scp command is the argument($1)
2)Run script from your machine:
#!/bin/bash
script='
#Your commands
'
sshpass -p<password> ssh user#host $script
And you have also another ways to run script to do sth with remote machine.
So, I've established a connection via ssh to a remote machine; and now what I would like to do is to execute few commands, grab some files and copy them back to my host machine.
I am aware that I can run
ssh user#host "command1; command2;....command_n"
and then close the connection, but how can I do the same without use the aforememtioned syntax? I have a lot of complex commands that has a bunch of quote and characters that would be a mess to escape.
Thanks!
My immediate thought is why not create a script and push it over to the remote machine to have it run locally in a text file? If you can't for whatever reason, I fiddled around with this and I think you could probably do well with a HEREDOC:
ssh -t jane#stackoverflow.com bash << 'EOF'
command 1 ...
command 2 ...
command 3 ...
EOF
and it seems to do the right thing. Play with your heredoc to keep your quotes safe, but it will get tricky. The only other thing I can offer (and I totally don't recomend this) is you could use a toy like perl to read and write to the ssh process like so:
open S, "| ssh -i ~/.ssh/host_dsa -t jane#stackoverflow.com bash";
print S "date\n"; # and so on
but this is a really crummy way to go about things. Note that you can do this in other languages.
Instead of the shell use some scripting language (Perl, Python, Ruby, etc.) and some module that takes care of the ugly work. For example:
#!/usr/bin/perl
use Net::OpenSSH;
my $ssh = Net::OpenSSH->new($host, user => $user);
$ssh->system('echo', 'Net::Open$$H', 'Quot%$', 'Th|s', '>For', 'You!');
$ssh->system({stdout_file => '/tmp/ls.out'}, 'ls');
$ssh->scp_put($local_path, $remote_path);
my $out = $ssh->capture("find /etc");
From here: Can I ssh somewhere, run some commands, and then leave myself a prompt?
The use of an expect script seems pretty straightforward... Copied from the above link for convenience, not mine, but I found it very useful.
#!/usr/bin/expect -f
spawn ssh $argv
send "export V=hello\n"
send "export W=world\n"
send "echo \$V \$W\n"
interact
I'm guessing a line like
send "scp -Cpvr someLocalFileOrDirectory you#10.10.10.10/home/you
would get you your files back...
and then:
send "exit"
would terminate the session - or you could end with interact and type in the exit yourself..
I have roughly 12 computers that each have the same script on them. This script merely pings all the other machines, and prints out whether the machine is "reachable" or "unreachable". However, it is inefficient to login to each machine manually using ssh to execute this script.
Suppose I'm logged into node 1. Is there any way to for me to login to node 2-12 automatically using SSH, execute the ping script, pipe the results to a file, logout and proceed to the next machine? Some kind of bash shell script?
I'm afraid I'm at a loss here since I haven't had experience with shell-scripting before.
Since the script is on the other machines, you can just have ssh run the command for you there:
ssh $hostname my_script >> results_file
When you specify a command like that, it's executed instead of the login shell.
I'll leave it up to you to figure out how to loop over hostnames!
One trick you'll need to use is setting up pre-authorized keys for each host. Then you can run a script on one host, running something like 'ssh hostname command > log.hostname'
This script might be what you are looking for: It allows you to execute one command (which can be your script) on multiple remote machines via ssh. It's a simple script with bash source available, so you should be able to customize it to your needs:
http://www.heinzi.at/projects/upgradebest.sh/
Yes you can
You need actually 2 small scripts as following:
remote_ssh.sh ( which takes as first argument the name of the machine and the rest of the arguments are your script that you want to execute with his own arguments)
Example : remote_ssh.sh node5 "echo hello world"
remote_ssh.sh as following:
#!/bin/bash
ALL_ARG=$#
FST_ARG=$1
REST_ARG=${ALL_ARG##$FST_ARG}
echo "Executing REMOTE COMMAND ON $FST_ARG"
/usr/bin/ssh $FST_ARG bash execute_ssh_command.sh $FST_ARG pwd $REST_ARG
execute_ssh_command.sh as following :
#!/bin/bash
ALL_ARG=$#
FST_ARG=$1
DIR_ARG=$2
REM_ARG="$1 $2"
REST_ARG=${ALL_ARG##$REM_ARG}
cd $DIR_ARG
$REST_ARG
of course you have to get this 2 scripts in your path of all your nodes ( maybe ~/bin/ )
Hope that it's helpful