Bashes PPA for testing scripts on Travis CI

A few months ago I released two Bash libraries for parsing command-line options. One is a pure Bash drop-in replacement for GNU getopt called pure-getopt, since GNU getopt isn’t always available, particularly on OS X. The other library is called ghettopt, and it’s designed to make command-line parsing much easier than calling getopt manually.

Each of these libraries has a test suite which is designed to be called from the command-line like this:

$ bash test.bash

This generates some human-readable output then exits with zero status if everything passed. Here’s an example from ghettopt:

$ bash test.bash
(nothing) ... pass
--foo ... pass
--foo=x ... pass
--foo x ... pass
--foo=x\ y ... pass
--bar=two ... pass
--bool ... pass
--no-bool ... pass
--bule ... pass
--no-bule ... pass
--arr=x --arr=y ... pass
--help ... pass
--help= ... pass
--colon=value ... pass
x y\ z ... pass
-- --bool ... pass

16 pass, 0 fail

$ echo $?
0

By setting the exit status to indicate overall pass/fail, this follows the pattern of other test suites, and it’s easy to plug into Travis CI, simply creating .travis.yml as follows:

language: bash
script: bash test.bash

Great, now we’re testing on Travis with every push to Github! But what about testing different versions of Bash? Python and other languages get explicit support for testing with multiple versions but there’s no provision for Bash. And yet it’s important⁠—Bash has changed dramatically from version to version, especially with the addition of associative arrays and regular expression matching. My initial implementations of both pure-getopt and ghettopt weren’t backward compatible to Bash version 2, but there are plenty of older installations, especially in shared hosting, where Bash 2.05b is still the system default.

Even though Travis doesn’t have explicit support for non-system Bash versions out of the box, it does provide package installation using apt, so we can install older Bash versions that way. In fact, we can also test newer Bash versions too, since we have no idea what version is installed by default on the Travis build boxes, and we needn’t care.

I’ve made a “bashes” PPA available. You can use it with something like this in .travis.yml:

env:
  - BASHES="bash2.05b bash3.0.16 bash3.2.48 bash4.2.45"
before_install:
  - echo | sudo add-apt-repository ppa:agriffis/bashes
  - sudo apt-get update -qq
  - sudo apt-get install -qq $BASHES

This installs all the available Bash versions simultaneously, which is fine because the names are versioned, for example /usr/bin/bash2.05b.

The trick now is to run the test suite multiple times, once with each version. One option is to use Travis’s built-in support for running a matrix of tests, but I don’t recommend that because it instantiates a virtual machine for each cell in the matrix. Assuming your test suite is small and you don’t anticipate pollution between runs, it’s gentler on the Travis infrastructure to instantiate a single VM and run the suite multiple times sequentially.

For that we can use a wrapper script which we’ll call travis.bash. This relies on the BASHES environment variable that we set in .travis.yml above.

#!/bin/bash

status=0

for b in $BASHES; do
    echo
    echo ==================
    echo $b
    echo ==================
    $b test.bash || status=$?
done

exit $status

So our final and complete .travis.yml contains:

language: bash
env:
  - BASHES="bash2.05b bash3.0.16 bash3.2.48 bash4.2.45"
before_install:
  - echo | sudo add-apt-repository ppa:agriffis/bashes
  - sudo apt-get update -qq
  - sudo apt-get install -qq $BASHES
script: bash travis.bash

If you use this to test your scripts, please let me know in the comments!

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