openssh unix dev - Dec 2009 - How to modify environment variables before executing a command

Hi,

I'd like to access and modify shell environment variables before
executing a command on a remote host via ssh. Unfortenatly, I can't
figure out the proper way to do this...

It seems, standard shell configuration files (e.g. ~/.bash_profile) are
not sourced before ssh executes a command. Of course I could explicitly
source them, e.g.
    ssh user at host 'source ~/.bash_profile; command'
But I don't like that because it delegates a server side configuration
task to the clients.

Is there a way to achieve this in a more general fashion on a per user
basis? I tried both ~/.ssh/environment and ~/.ssh/rc, as documented in
the man page. But ~/.ssh/environment only works for static variables and
I didn't manage to export variables defined in ~/.ssh/rc.

For example, if I have these files in my home directory on server
    # ~/.ssh/environment
    VAR1=$(date)
and
    # ~/.ssh/rc
    VAR2=$(date)
    export VAR2
then executing env from the client via
    ssh malte at server env | grep VAR
will result in
    VAR1=$(date)
i.e., VAR1 is passed literally while VAR2 is not available.

And where are the variables defined that I see when exexuting
    ssh user at server env
Among them are
    SHELL=/bin/bash
    PWD=/home/malte

Thanks in advance,
Malte

>> I'd like to access and modify shell environment variables before
>> executing a command on a remote host via ssh. Unfortenatly, I can't
>> figure out the proper way to do this...
Thanks for the suggestions I received!

Karlan T. Mitchell schrieb:
> ~/.bashrc I believe.  Profile is for local terminals.....pretty sure at
> least. Hope this helps
Jim Rees schrieb:
> The bash man page suggests you should be able to do this:
> ~/.ssh/environment
> BASH_ENV=.bash_profile
I extended my test scenario to four configuration files on the server:
    # .ssh/environment
    VAR1=$(date)
    BASH_ENV=~/.ssh/ssh_profile

    # .ssh/rc
    echo ".ssh/rc"
    VAR2=$(date)
    export VAR2

    # .bashrc
    echo ".bashrc"
    VAR3=$(date)
    export VAR3

    # ~/.ssh/ssh_profile
    echo ".ssh/ssh_profile"
    VAR4=$(date)
    export VAR4

Now, when I execute
    $ ssh server env | grep -E -e '^\.' -e VAR
I get
    .ssh/ssh_profile
    .ssh/rc
    .bashrc
    VAR1=$(date)
    VAR3=Mi 2. Dez 18:16:33 CET 2009
So all four files are read or sourced, respectively.

I hadn't noticed that ~/.bashrc is sourced because it starts with
    # If not running interactively, don't do anything
    [ -z "$PS1" ] && return
which terminates it in the ssh context. But above that test I could
insert a test for some flag set in .ssh/environment and setup the shell
variables I need for ssh. Still, that seems a little awkward as .bashrc
is sourced every time any shell is created with the default
configuration files.

I'm still looking for a more ssh-specific solution. Unfortenately, the
variables exported from the two ssh-specific files .ssh/rc and
.ssh/ssh_profile don't make it into the environment. Why is that?

A secondary problem with using BASH_ENV could be that its value is
evaluated by every non-interactive shell. So, if I use ssh to login to
the server and then run a script with bash, the file specified by
BASH_ENV is sourced. For example, with the above setup:
    $ echo "echo foo" > say_foo.sh
    $ bash say_foo.sh
    .ssh/ssh_profile
    foo

Any more suggestions on how to modify environment variables before
executing a command via ssh?

Thanks, Malte

Malte Forkel wrote:
> Any more suggestions on how to modify environment variables before
> executing a command via ssh?
You can use SendEnv in the client configuration. But the server must
also AcceptEnv those same variables.


//Peter

Malte Forkel wrote:
> 
> Any more suggestions on how to modify environment variables before
> executing a command via ssh?
> 
SSH will set the SSH_CLIENT, SSH_TTY and SSH_CONNECTION
So you can tell if this is an ssh session.

~./.bashrc is always run, and $- on my Ubuntu is hBc
the first time. If its interactive, ~/.bash_profile is then run and
$- is himBH.

Some systems might run /etc/profile as well, so tests are needed
try echo $-

So your .bashrc could test for SSH_CLIENT,and $- for c
and set what it wants. It could also set MY_ENV_HAS_BEEN_SET=1
so you only run you code once at the start of a session.
> Thanks, Malte
> 
> 
> 
> 
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