bash configuration templating

Question

I am using a bash script to install and configuration an application. I am trying to use a template where I can fill in values from variables and then save it to its proper location. This works fine with just variables, but I am unable to use any conditionals. Are there any better ways of doing this?

Heres my example template:

    #!/bin/bash

    cat <<EOF
    DEFAULTS: &DEFAULTS
      adapter: $DB
      host: $DB_HOST
      username: $DB_USER
      password: $DB_PASS
      database: $DB_DATABASE
      if [ ! $DB_RECONNECT = ""]; then
        reconnect: $DB_RECONNECT
      fi
      if [ ! $DB_TIMEOUT = ""]; then
        timeout: $DB_TIMEOUT  
      fi
    EOF

And then I use source template.sh > /path/to/file to evaluate and save the file.

think about what's happening, would you expect a cated file to execute? That's what your doing right?, except that the source of the file to cat is provided by the <<EOF here-document. So why not follow your source template > file with chmod 755 file; ./file to execute the logic inside? — shellter
– shellter, Commented Nov 15, 2012 at 16:18

doubleDown · Accepted Answer · 2012-11-15 18:14:26Z

1

You don't have to enclose everything in the heredoc

cat <<EOF
...
database: $DB_DATABASE
EOF

if [ -z "$DB_RECONNECT" ]; then
    echo "reconnect: $DB_RECONNECT"
fi

if [ -z "$DB_TIMEOUT" ]; then
    echo "timeout: $DB_TIMEOUT"
fi

answered Nov 15, 2012 at 18:14

doubleDown

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1 Comment

Capt.Redbeard Over a year ago

I didn't even think of doing it that way... Thanks.

Gilles Quénot · Accepted Answer · 2012-11-15 14:39:01Z

0

You can use the command tpage like in this simple example :

$ cat /tmp/l.tpl 
DEFAULTS: [%def%]
    adapter[%db%]

$ tpage --define def=foo --define db=bar --interpolate /tmp/l.tpl
DEFAULTS: foo
    adapterbar

tpage is a command coming with the well known Perl module Template::Toolkit, but no need to know Perl to use it. You can do some conditional as well, see conditional

Project : http://www.template-toolkit.org/

answered Nov 15, 2012 at 14:39

Gilles Quénot

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