Bash script woes

I had an opportunity to play with Bash script on Friday. My task was to write a small deployment script to grab our server class configuration settings from subversion and rsync them to the appropriate machines.

This was easy enough, a couple of commands to subversion, rsync and some glue and I’d be done. However, an hour into writing it I wish I’d used PHP or used my time to learn how to do it in Perl.

For one, a hash of arrays doesn’t sit well in Bash script. I wanted to define a list of servers for each class. In PHP the code would have been as simple as:

<?php

$servers = array(
  'web' => array('server1', 'server2', 'server3'),
  'db'  => array('server4', 'server5', 'server6')
);

?>

Fortunately I was able to work around this with separate arrays for each class. What I couldn’t get around was the pain I had to endure to pass an array as an argument to a function.

Passing an array involves loading the space-separated elements of the array into a variable with command substitution.

Taken from Chapter 33 of the Advanced Bash-Scripting Guide.

printarray () {
  local passed_array
  passed_array=( `echo "$1"` )
  echo "${passed_array[@]}"
}

original_array=( element1 element2 element3 element4 element5 )
argument=`echo ${original_array[@]}` # command substitution
printarray "$argument"

This is just clunky and showed me that for anything more than basic conditional logic I’m better off investing some time in learning Perl.