Passing variables in remote ssh command

Question

I want to be able to run a command from my machine using ssh and pass through the environment variable  BUILD NUMBER  Here s what I m trying   ssh pvt 192 168 1 133    tools myScript pl  BUILD NUMBER     BUILD NUMBER is set on the machine making the ssh call and since the variable doesn t exist on the remote host  it doesn t get picked up   How do I pass the value of  BUILD NUMBER

User · Answer

Escape the variable in order to access variables outside of the ssh session      ssh pvt 192 168 1 133    tools myScript pl   BUILD NUMBER

User · Answer

If you use  ssh pvt 192 168 1 133    tools run pvt pl  BUILD NUMBER    instead of  ssh pvt 192 168 1 133    tools run pvt pl  BUILD NUMBER    your shell will interpolate the  BUILD NUMBER before sending the command string to the remote host

User · Answer

It is also possible to pass environment variables explicitly through ssh  It does require some server-side set-up through  so this this not a universal answer   In my case  I wanted to pass a backup repository encryption key to a command on the backup storage server without having that key stored there  but note that any environment variable is visible in ps  The solution of passing the key on stdin would work as well  but I found it too cumbersome  In any case  here s how to pass an environment variable through ssh   On the server  edit the sshd config file  typically  etc ssh sshd config and add an AcceptEnv directive matching the variables you want to pass  See man sshd config  In my case  I want to pass variables to borg backup so I chose   AcceptEnv BORG     Now  on the client use the -o SendEnv option to send environment variables  The following command line sets the environment variable BORG SECRET and then flags it to be sent to the client machine  called backup   It then runs printenv there and filters the output for BORG variables     BORG SECRET magic-happens ssh -o SendEnv BORG SECRET backup printenv   egrep BORG BORG SECRET magic-happens

User · Answer

As answered previously  you do not need to set the environment variable on the remote host  Instead  you can simply do the meta-expansion on the local host  and pass the value to the remote host   ssh pvt 192 168 1 133    tools run pvt pl  BUILD NUMBER    If you really want to set the environment variable on the remote host and use it  you can use the env program  ssh pvt 192 168 1 133  env BUILD NUMBER  BUILD NUMBER   tools run pvt pl   BUILD NUMBER    In this case this is a bit of an overkill  and note   env BUILD NUMBER  BUILD NUMBER does the meta expansion on the local host the remote BUILD NUMBER environment variable will be used by the remote shell

User · Answer

This answer might seem needlessly complicated  but it   s easily extensible and robust regarding whitespace and special characters  as far as I know    You can feed data right through the standard input of the ssh command and read that from the remote location   In the following example    an indexed array is filled  for convenience  with the names of the variables whose values you want to retrieve on the remote side  For each of those variables  we give to ssh a null-terminated line giving the name and value of the variable  In the shh command itself  we loop through these lines to initialise the required variables      Initialize examples of variables    The first one even contains whitespace and a newline  readonly FOO   apjlljs ailsi  n ajlls t   jij  readonly BAR ygn  gy    ynygbjrbjrb    Make a list of what you want to pass through SSH     The    unset    is just in case someone exported   an associative array with this name   unset -v VAR NAMES readonly VAR NAMES       FOO     BAR    for name in    VAR NAMES      do     printf   s  s 0    name      name   done   ssh user somehost com       while read -rd        name value     do         export   name    value      done        Check     printf  FOO     q   BAR     q  n    FOO    BAR      Output   FOO      apjlljs ailsi  n ajlls t   jij    BAR    ygn  gy    ynygbjrbjrb    If you don   t need to export those  you should be able to use declare instead of export   A really simplified version  if you don   t need the extensibility  have a single variable to process  etc   would look like     ssh user somehost com  read foo   lt  lt  lt    foo

User · Answer

Variables in single-quotes are not evaluated   Use double quotes   ssh pvt 192 168 1 133    tools run pvt pl  BUILD NUMBER    The shell will expand variables in double-quotes  but not in single-quotes   This will change into your desired string before being passed to the ssh command

User · Answer

The list of accepted environment variables on SSHD by default includes LC    Thus   LC MY BUILDN  1 2 3  ssh -o  SendEnv LC MY BUILDN  ssh-host  echo  LC MY BUILDN  1 2 3

[linux] Passing variables in remote ssh command

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