linux - Unable to get profile variable using ssh

Unable to retrieve the profile variable using ssh.

server2 ==> user apptst ==> bash profile has $APPHOME variable.

Was trying to retrieve the value from server1 using ssh but failed.

Used options below

server1> ssh apptst@server2 'echo $APPHOME'

server1> ssh apptst@server2 echo '$APPHOME'

server1> ssh apptst@server2 echo "$APPHOME"

server1> ssh apptst@server2 "echo $APPHOME"

when tried

server1> ssh apptst@server2 ls -ld $APPHOME

it works fine.

Any suggestions what is missing and how can I get the variable from server2?

Answer

This command should work:

 server1> ssh apptst@server2 'bash -l -c "echo \$APPHOME"'

• you need ' quotes to pass that complete command to ssh as one argument; this also prevents the shell on server1 to expand $APPHOME itself


• bash -l starts a login shell, which reads in the profiles files, where $APPHOME gets defined (as @chepner pointed out in his answer, this is not default when invoked by sshd)


• -c executes the next argument, again with quotes that the complete echo command gets executed.


• escaping \$ is necessary, because otherwise the parent (non-login) shell which sshd invokes (and which inherits the environment diretly from init (*)) does expand $APPHOME. But this is too early as $APPHOME only gets defined for login shells (via ~/.profile). [added this point after comment from OP]

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(*) correct me, if I'm wrong here.