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I'm playing around with duplicity via a script that looks like this:

export PASSPHRASE=SomeLongGeneratedHardToCrackKey
duplicity /etc scp://[email protected]/etc
unset PASSPHRASE

Here's a link to the ubuntu documentation.

If I want to set the PASSPHRASE from the command line instead of setting it from the script how do I do that?

I tried (Via the command line):

PASSPHRASE='SomeLongGeneratedHardToCrackKey'

export -n PASSPHRASE

However this does not work. Duplicity still asks me to enter the passphrase for the gpg key.

Thoughts? TIA,

Ole

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  • Lose the -n (see (help export) for details). Commented May 14, 2016 at 21:41

1 Answer 1

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Shells are designed so that scripts and interactive command line sessions look the same. That means that you can effectively retype:

export PASSPHRASE=SomeLongGeneratedHardToCrackKey
duplicity /etc scp://[email protected]/etc
unset PASSPHRASE

Since exporting for variables for a particular command only is common, there's a shortcut for it:

PASSPHRASE=SomeLongGeneratedHardToCrackKey \
duplicity /etc scp://[email protected]/etc

export -n doesn't work because export -n is the opposite of export as help export explains:

 ...
  -n    remove the export property from each NAME
 ...
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  • FOO=bar mycmd args would not make FOO an environment variable; it just restricts the variable in this particular line. It is the same as FOO=bar, mycmd args and then unset FOO. To export it for mycmd (duplicity here), use env, like env FOO=bar mycmd args. Commented May 15, 2016 at 4:17
  • @FranklinYu FOO=bar mycmd args will absolutely make FOO an environment variable restricted to mycmd. You don't need env for that. Commented May 15, 2016 at 8:13
  • @FranklinYu printf '%s\n' "#!/bin/bash" "declare -p FOO" > printfoo && chmod +x printfoo && FOO=bar ./printfoo will give you declare -x FOO="bar". If that -x isn't proof enough to you FOO=bar env |grep FOO should be. If this syntax didn't use environment variables it, would be restricted to shell functions and builtins because there's no way that an non-environment variable would get to an execed process. Commented May 15, 2016 at 8:27
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    thank you for your hint. I just verified that you are correct about that; FOO=bar mycmd args and env FOO=bar mycmd args seems exactly the same. I guess the only advantage of using env would be that -i of env can erase all inherited environment variables. Sorry for posting comments without verifying. Commented May 15, 2016 at 18:26

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