Support reading config vars from ENV

[nicdoye]

In addition to --baseurl, I'd like to be able to pass the site title. Other people may have use cases for other options that are normally set in config.toml etc.

Is this a worthy enhancement?

Command line arguments appear to be set in [initHugoBuildCommonFlags()] in commands/hugo.go but I can't see immediately where they're merged with the config contents.

An alternative would be to use environment variables, but I don't think Hugo uses them at all.

Note: In Jekyll, I currently do this by abusing ENV['JEKYLL_ENV'] and using {{jekyll.environment}} (there may be a "correct" way, but I don't know it).

[bep]

An alternative would be to use environment variables, but I don't think Hugo uses them at all.

I'm pretty sure you can set config vars from environment vars. See https://github.com/spf13/viper ... if it doesn't work, Viper is the correct repo to report issues about it.

We will not create flags for all the config.

[nicdoye]

Thank you. Apologies for not having looked at viper to work it out.

[bep]

No problem - and don't hesitate to revisit this issue if you don't get it working.

[nicdoye]

I don't think environment variables are currently set up in hugo. Testing $BASEURL (as an example, because it's already accepted by --baseurl) doesn't work.

Adding a quick hack of

snagglepuss:~ nic$ diff -bu GitHub/hugo/commands/hugo.go Go/src/github.com/spf13/hugo/commands/hugo.go
--- GitHub/hugo/commands/hugo.go    2016-04-18 15:36:28.000000000 +0100
+++ Go/src/github.com/spf13/hugo/commands/hugo.go   2016-04-18 15:27:24.000000000 +0100
@@ -334,6 +334,8 @@
    }

    viper.RegisterAlias("indexes", "taxonomies")
+        viper.SetEnvPrefix("hugo")
+        viper.AutomaticEnv()

    loadDefaultSettings()

Allows me to run

HUGO_TITLE='Example Title' HUGO_BASEURL='http://example.com' /Users/nic/Go/src/github.com/spf13/hugo/hugo

Obviously:

• the SetEnvPrefix() wasn't necessary;
• the two lines may not be in the right place;
• AutomaticEnv() may not be exactly the right thing should you wish to enable environment variables;
• you may still not want to enable environment variables.

[bep]

OK, I calling AutomaticEnv() works ... but Hugo has a lot of very generic variable names, so without any namespace this will get confusing. Will have to think about this. @spf13 might chime in with an idea.

[bep]

Never mind, I misunderstood the prefix feature. That solves it. Will fix.

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