Shell linter evaluation and usage –

Tomorrow, the 1st of August is a national holiday in Switzerland … So I do one day off and have some time. For a long time I wanted to deal with Shell lint. After some research, i found a few open-source tools. By the way … linters are being written for many programming languages and document formats.

Preparation

For evaluation i will not install the tools on my local system,… so Vagrant (with CentOS 7) is my choice.

# create project
$ mkdir -p ~/Projects/ShellLint && cd ~/Projects/ShellLint

# create example.sh
$ vim example.sh

# create Vagrantfile
$ vim Vagrantfile

#!/bin/bash

declare -r VERSION="1.0.0"
declare -r FILE_NAME=$(basename "$0")

function fc_usage()
{
 printf "Usage: %s" "$FILE_NAME"
 printf " [-h] [-V]\n"
}

function failure()
{
 print "here is a error"

syntax() {
 print "this line has simply to many chars ... with a simple shell lint you should see"
}

function fc_bashism()
{
 echo -e "hello world"
}

function main()
{
 fc_usage
 fc_bashism
}

exit 0

# -*- mode: ruby -*-
# vi: set ft=ruby :

Vagrant.configure("2") do |config|
  config.vm.box = "lupin/centos7"
  config.vm.box_check_update = false
  config.vm.synced_folder '.', '/vagrant', disabled: true

  config.vm.provision "file", source: "example.sh", destination: "example.sh"

  config.vm.provider "virtualbox" do |vb|
    vb.gui = false
    vb.name = "ShellLint"
    vb.memory = "1024"
    vb.cpus = 1
  end

end

Note: I created the Vagrant box “lupin/centos” via Packer … here my GitHub repository.

# create environment
$ vagrant up

# SSH into VM
$ vagrant ssh

Shell option -n

Many shell’s already offer a very simple script analysis. The option -n read commands in script, but do not execute them (syntax check).

# example bash
$ bash -n example.sh

# example shell
$ sh -n example.sh

Okay … but not really what I want… (more details are welcome)

shlint and checkbashisms

I found the repository here.

# install ruby (optional)
$ yum install -y ruby

# install json_pure (optional)
$ gem install json_pure

# install shlint
$ gem install shlint

# create config
$ echo -e 'shlint_shells="bash sh"\nshlint_debug=1' > .shlintrc

# run shlint
$ shlint example.sh

# run checkbashisms
$ checkbashisms -f example.sh

Note: for both tools you should change the shebang to “#!/bin/sh”

For shlint… I don’t get it. For checkbashisms … good if will write portable Shell scripts.

bashate

I found it here on Pypi.

# install epel repository
$ yum install -y epel-release

# install pip (python 2.x)
$ yum install -y python2-pip

# install bashate
$ pip install bashate

# run bashate
$ bashate example.sh

Nice … but not really all Standards.

Shellsheck

Shellcheck is known! Here the online service and here the repository.

# install epel repository
$ yum install -y epel-release

# update (optional)
$ yum update -y

# install ShellCheck
$ yum install -y ShellCheck

# run ShellCheck
$ shellcheck example.sh

I stay with that tool. Currently there are packages for almost every known OS.

Additional

Who knows me … knows that I do not like Installer and prefer Docker use. Here’s some fun.

# exit Vagrant and destroy
$ vagrant halt && vagrant destroy -f

# create Dockerfile
$ vim Dockerfile

# create Applescript
$ vim linter.scpt

# build Docker image
$ docker build -t alpine/shellcheck .

# change permission
$ chmod +x linter.scpt

# run Applescript
$ osascript linter.scpt

FROM alpine:latest

# install needed packages
RUN apk --update add wget

# download archive
RUN wget -q --no-check-certificate https://storage.googleapis.com/shellcheck/shellcheck-latest.linux.x86_64.tar.xz

# unzip archive
RUN tar xvfJ shellcheck-latest.linux.x86_64.tar.xz

# move binary
RUN mv /shellcheck-latest/shellcheck /usr/local/bin/shellcheck

# cleanup
RUN apk del wget
RUN rm -f shellcheck-latest.linux.x86_64.tar.xz
RUN rm -fr shellcheck-latest/

# change to mount directory
WORKDIR /mnt

# set entrypoint
ENTRYPOINT ["/usr/local/bin/shellcheck"]

#!/usr/bin/osascript

-- define global variables
global appName
global imageName

-- set magic values
set appName to "Docker"
set imageName to "alpine/shellcheck "

-- run docker linters
on LintShell(macPath)
	set posixPath to quoted form of POSIX path of macPath
	set fileName to do shell script "basename " & posixPath
	set dirName to do shell script "dirname " & posixPath
	set shellCmd to "docker run --rm -i -v " & dirName & ":/mnt " & imageName & fileName

	tell application "Terminal"
		set shell to do script shellCmd in front window
	end tell
end LintShell

-- display select box
on SelectFile()
	set dlTitle to "Nothing selected..."
	set dlMsg to "Process is terminated."

	try
		set macPath to choose file
	on error
		display dialog dlMsg buttons ["OK"] with title dlTitle
		return dlMsg
	end try

	LintShell(macPath)
end SelectFile

-- start Docker
on StartDocker()
	set dlTitle to "Docker cannot started"
	set dlMsg to "Something went wrong, could not start Docker!"

	try
		tell application appName
			activate
		end tell
	on error
		display dialog dlMsg buttons ["OK"] with title dlTitle
	end try
end StartDocker

-- check if Docker is running
on RunScript()
	set dlTitle to "Docker not running"
	set dlMsg to "Should Docker started?"

	if application appName is running then
		SelectFile()
	else
		display dialog dlMsg buttons ["OK", "No"] with title dlTitle
		if button returned of result is "OK" then
			StartDocker()
		end if
	end if
end RunScript

RunScript()

😉 just for fun…

– Softwaretester –

knowledge is power

Shell linter evaluation and usage