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binaryphile's solution

to Hello World in the Bash Track

Published at Sep 15 2018 · 0 comments
Instructions
Test suite
Solution

The classical introductory exercise. Just say "Hello, World!".

"Hello, World!" is the traditional first program for beginning programming in a new language or environment.

The objectives are simple:

  • Write a function that returns the string "Hello, World!".
  • Run the test suite and make sure that it succeeds.
  • Submit your solution and check it at the website.

If everything goes well, you will be ready to fetch your first real exercise.

Welcome to Bash!

Unlike many other languages here, bash is a bit of a special snowflake. If you are on a Mac or other unix-y platform, you almost definitely already have bash. In fact, anything you type into the terminal is likely going through bash.

The downside to this is that there isn't much of a development ecosystem around bash like there is for other languages, and there are multiple versions of bash that can be frustratingly incompatible. Luckily we shouldn't hit those differences for these basic examples, and if you can get the tests to pass on your machine, we are doing great.

Installation

As mentioned above, if you are on a unix-like OS (Mac OS X, Linux, Solaris, etc), you probably already have bash.

Testing

As there isn't much of a bash ecosystem, there also isn't really a de facto leader in the bash testing area. For these examples we are using bats. You should be able to install it from your favorite package manager, on OS X with homebrew this would look something like this:

$ brew install bats
==> Downloading
https://github.com/sstephenson/bats/archive/v0.4.0.tar.gz
==> Downloading from
https://codeload.github.com/sstephenson/bats/tar.gz/v0.4.0
########################################################################
100.0%
==> ./install.sh /opt/boxen/homebrew/Cellar/bats/0.4.0
🍺  /opt/boxen/homebrew/Cellar/bats/0.4.0: 10 files, 60K, built in 2
seconds

Run the tests with:

bats hello_world_test.sh

After the first test(s) pass, continue by commenting out or removing the skip annotations prepending other tests.

Source

This is an exercise to introduce users to using Exercism http://en.wikipedia.org/wiki/%22Hello,_world!%22_program

External utilities

Bash is a language to write scripts that works closely with various system utilities, like sed, awk, date and even other programming languages, like Python. This track does not restrict the usage of these utilities, and as long as your solution is portable between systems and does not require installing third party applications, feel free to use them to solve the exercise.

For an extra challenge, if you would like to have a better understanding of the language, try to re-implement the solution in pure Bash, without using any external tools.

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

hello_world_test.sh

#!/usr/bin/env bash

@test "Say Hi!" {
  run bash hello_world.sh

  [ "$status" -eq 0 ]
  [ "$output" = "Hello, World!" ]
}
#!/usr/bin/env bash

# http://www.binaryphile.com/bash/2018/07/26/approach-bash-like-a-developer-part-1-intro.html

IFS=$'\n'
set -o noglob

main () {
  hello_world
}

hello_world () {
  echo "Hello, World!"
}

sourced? () {
  [[ ${FUNCNAME[1]} == source ]]
}

strict_mode () {
  case $1 in
    on  ) set -euo pipefail;;
    off ) set +euo pipefail;;
  esac
}

sourced? && return
strict_mode on

main $*

Community comments

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What can you learn from this solution?

A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that you could read more about to improve your understanding?