I expected it to print v=1. Why does this print v=?
cat<<DONE|ssh user#host
v=1
echo v=$v
DONE
On host, bash is the shell.
Your code is equivalent to:
echo "v=1;echo v=$v"|ssh user#host
What you want is:
echo 'v=1;echo v=$v'|ssh user#host
You can achieve this by using cat<<'DONE' instead of cat<<DONE.
Variables are expanded inside heredocs. You need to escape the $ with a \
Related
I want to run some commands each time when I log in to a remote system. Storing commands in .bashrc on remote is not an option.
What is the proper way to escape the escape chars inside of quotes in bash script for ssh?
How can I write each command in new line?
My script
#!/bin/bash
remote_PS1=$'\[\033[01;32m\]\u#\[\033[03;80m\]\h\[\033[00m\]:\[\033[01;34m\]\!:\w\[\033[00m\]\$ '
ssh -t "$#" 'export SYSTEMD_PAGER="";' \
'export $remote_PS1;' \
'echo -e "set nocompatible" > /home/root/.vimrc;' \
'bash -l;'
didn't work.
Escaping escape characters inside double-quotes and run them on remote server is way too complicated for me :)
Instead, I wrote a remoterc file for remote and a small remotessh script.
In remotessh, first I copy remoterc on remote machine and run bash command with that remoterc file interactively.
remoterc:
#!/bin/bash
SYSTEMD_PAGER=""
PS1="\[\033[01;32m\]\u#\[\033[03;80m\]\h\[\033[00m\]:\[\033[01;34m\]\!:\w\[\033[00m\]\$ "
echo -e "set nocompatible" > /home/root/.vimrc
remotessh:
#!/bin/bash
scp remoterc "$1":/home/root/
ssh "$1" -t "bash --rcfile remoterc -i"
It works :)
You can use Bash's printf %q.
According to help printf:
%q quote the argument in a way that can be reused as shell input
See the following example:
$ cat foo.sh
ps1='\[\033[1;31m\]\u:\w \[\033[0m\]\$ '
ps1_quoted=$( printf %q "$ps1" )
ssh -t foo#localhost \
'export FOO=bar;' \
"export PS1=$ps1_quoted;" \
'bash --norc'
Result:
Below is an example of a ssh script using a heredoc (the actual script is more complex). Is it possible to use both local and remote variables within an SSH heredoc or command?
FILE_NAME is set on the local server to be used on the remote server. REMOTE_PID is set when running on the remote server to be used on local server. FILE_NAME is recognised in script. REMOTE_PID is not set.
If EOF is changed to 'EOF', then REMOTE_PID is set and `FILE_NAME is not. I don't understand why this is?
Is there a way in which both REMOTE_PID and FILE_NAME can be recognised?
Version 2 of bash being used. The default remote login is cshell, local script is to be bash.
FILE_NAME=/example/pdi.dat
ssh user#host bash << EOF
# run script with output...
REMOTE_PID=$(cat $FILE_NAME)
echo $REMOTE_PID
EOF
echo $REMOTE_PID
You need to escape the $ sign if you don't want the variable to be expanded:
$ x=abc
$ bash <<EOF
> x=def
> echo $x # This expands x before sending it to bash. Bash will see only "echo abc"
> echo \$x # This lets bash perform the expansion. Bash will see "echo $x"
> EOF
abc
def
So in your case:
ssh user#host bash << EOF
# run script with output...
REMOTE_PID=$(cat $FILE_NAME)
echo \$REMOTE_PID
EOF
Or alternatively you can just use a herestring with single quotes:
$ x=abc
$ bash <<< '
> x=def
> echo $x # This will not expand, because we are inside single quotes
> '
def
remote_user_name=user
instance_ip=127.0.0.1
external=$(ls /home/)
ssh -T -i ${private_key} -l ${remote_user_name} ${instance_ip} << END
internal=\$(ls /home/)
echo "\${internal}"
echo "${external}"
END
This question already has answers here:
is it possible to use variables in remote ssh command?
(2 answers)
Closed 6 years ago.
I am trying to execute some shell script on a remote server via SSH.
Given below is a code sample:
ssh -i $KEYFILE_PATH ubuntu#$TARGET_INSTANCE_IP "bash" << EOF
#!/bin/bash
cat /home/ubuntu/temp.txt
string=$(cat /home/ubuntu/temp.txt )
echo $string
EOF
cat prints the expected result but
$string prints nothing.
How do I store the return value of cat in a variable?
You need to make the content of Here doc literal otherwise they will be expanded in the current shell, not in the desired remote shell.
Quote EOF:
ssh .... <<'EOF'
...
...
EOF
You should be able to simply do this:
ssh -i $KEYFILE_PATH ubuntu#$TARGET_INSTANCE_IP "bash" <<'_END_'
cat /home/ubuntu/temp.txt
string=$(cat /home/ubuntu/temp.txt)
echo $string
_END_
<<'_END_' ... _END_ is called a Here Document literal, or "heredoc" literal. The single quotes around '_END_' prevent the local shell from interpreting variables and commands inside the heredoc.
The intermediate shell is not required (assuming you use bash on the remote system).
Also you dont have to use an intermediate HERE-DOC. Just pass a multiline Command:
ssh -i $KEYFILE_PATH ubuntu#$TARGET_INSTANCE_IP '
cat /home/ubuntu/temp.txt
string=$(cat /home/ubuntu/temp.txt )
echo $string
'
Note I am using single quotes to prevent evaluation on the local shell.
I would like to connect to different shells (csh, ksh etc.,) and execute command inside each switched shell.
Following is the sample program which reflects my intention:
#!/bin/bash
echo $SHELL
csh
echo $SHELL
exit
ksh
echo $SHELL
exit
Since, i am not well versed with Shell scripting need a pointer on how to achieve this. Any help would be much appreciated.
If you want to execute only one single command, you can use the -c option
csh -c 'echo $SHELL'
ksh -c 'echo $SHELL'
If you want to execute several commands, or even a whole script in a child-shell, you can use the here-document feature of bash and use the -s (read commands from stdin) on the child shells:
#!/bin/bash
echo "this is bash"
csh -s <<- EOF
echo "here go the commands for csh"
echo "and another one..."
EOF
echo "this is bash again"
ksh -s <<- EOF
echo "and now, we're in ksh"
EOF
Note that you can't easily check the shell you are in by echo $SHELL, because the parent shell expands this variable to the text /././bash. If you want to be sure that the child shell works, you should check if a shell-specific syntax is working or not.
It is possible to use the command line options provided by each shell to run a snippet of code.
For example, for bash use the -c option:
bash -c $code
bash -c 'echo hello'
zsh and fish also use the -c option.
Other shells will state the options they use in their man pages.
You need to use the -c command line option if you want to pass commands on bash startup:
#!/bin/bash
# We are in bash already ...
echo $SHELL
csh -c 'echo $SHELL'
ksh -c 'echo $SHELL'
You can pass arbitrary complex scripts to a shell, using the -c option, as in
sh -c 'echo This is the Bourne shell.'
You will save you a lot of headaches related to quotes and variable expansion if you wrap the call in a function reading the script on stdin as:
execute_with_ksh()
{
local script
script=$(cat)
ksh -c "${script}"
}
prepare_complicated_script()
{
# Write shell script on stdout,
# for instance by cat-ting a here-document.
cat <<'EOF'
echo ${SHELL}
EOF
}
prepare_complicated_script | execute_with_ksh
The advantage of this method is that it easy to insert a tee in the pipe or to break the pipe to control the script being passed to the shell.
If you want to execute the script on a remote host through ssh you should consider encode your script in base 64 to transmit it safely to the remote shell.
I have bash script (for example):
ssh -t -t user#domain.com << EOF
cd /home/admin
mkdir test
echo 'Some text'
exit
EOF
Can I display only "echo" command in terminal? It is possible?
Now all commands are displayed.
Thank you
Specifying the commands on standard input with ssh -t causes the commands to be echoed back, but you don't have to do that.
ssh -t user#domain.com "
cd /home/admin
mkdir test
echo 'Some text'"
(The exit isn't really required or useful, so I left it out.)
Use single quotes if you want to prevent the local shell from interpolating variables etc in the string containing the commands.
To selectively display an individual command as well as its output, you can use something like
sh -vc 'echo \"Some text\"'
although the nested quoting can start getting on your nerves pretty quickly.