linux - Bash export command

Question

I am encountering a strange problem with my 64-bit Ubuntu - on the export command.

Basically, I have got a VM installation on Ubuntu on my Windows?7 system, and I am trying to pass commands from my Windows system to my VM installation using a custom (given by client) software.

So, on my VM, when I do:

export foo=bar
echo $foo

everything works as expected.

However, when I do the same through the custom software (which basically passes the Linux command as a string to the bash shell), I get:

export: command not found

I tried looking at the shell (using the custom software), using:

echo $SHELL > shell.txt

And I get /bin/bash which is expected and I still get the "export: command not found error".

How can I fix this?

Answer 1

export is a Bash builtin, echo is an executable in your $PATH. So export is interpreted by Bash as is, without spawning a new process.

You need to get Bash to interpret your command, which you can pass as a string with the -c option:

bash -c "export foo=bar; echo $foo"

ALSO:

Each invocation of bash -c starts with a fresh environment. So something like:

bash -c "export foo=bar"
bash -c "echo $foo"

will not work. The second invocation does not remember foo.

Instead, you need to chain commands separated by ; in a single invocation of bash -c:

bash -c "export foo=bar; echo $foo"