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Compare environment files in the Linux console

ยท 4 min read
Christophe

Compare environment files in the Linux console

This is a very common source of problems using .env files: you've two or more different .env file like .env and .env.example.

You're a programmer and coding a new amazing feature. You're adding one or more new environment variables to your local .env file and everything is working fine on your computer.

Boum! Your feature is buggy.

A colleague copy the source code from a versioning system like Github/GitLab or, second scenario, someone will deploy the feature on a server and your feature is broken.

Why? Because the variable(s) you've added have been added in your local .env file, on your computer only.

As you know, you have to create the variables in the .env.example file too but let's be honest, nobody thinks about it.

There are some tools that allow comparing two files like diff but not really the best here since:

  1. We don't care about comments and empty lines. If a variable has been commented, we just need to ignore it.
  2. We don't care about the position in the file where the variable is declared. If APP_ENV = local is on the first line, in the middle of the file or just before the last line, we don't care about it.
  3. We can also ignore some variables that we know they should be different like APP_KEY f.i.

Let's try... Below we'll create the file .env.example with two lines then copy it to .env and just add a new line in .env.example. Finally, we'll sort sort -o .env.example so the order will differs with .env.

mkdir -p /tmp/playing_env && cd $_

echo 'APP_NAME = My application' > .env.example
echo 'APP_ENV = local' >> .env.example

# Make .env and .env.example identical
cp .env.example .env

# Now just create a variable with a different value in both files
echo 'APP_KEY = 5a0678afd37f4b8d/8d9451a7381266e3' >> .env
echo 'APP_KEY = 3445118442a942d1/afd37466fadd5223' >> .env.example

# Add a new variable but only in the .env.example file
echo 'CACHE_DRIVER = redis' >> .env.example

# And sort .env.example so line ordering will differs with .env
sort -o .env.example .env.example

Now that we have our two files with some differences, we can run this command:

(
clear
ENV1=.env
ENV2=.env.example
printf "\e[33;1m%-63s %s\e[0;1m\n" "Left side: ${ENV1}" "Right side: ${ENV2}"
diff --suppress-common-lines -y \
<(grep -v -E '^#|^$' ${ENV1}| sort) \
<(grep -v -E '^#|^$' ${ENV2} | sort) \
| grep -v 'APP_KEY'
)

diff will compare the two files but not directly the file itself but the content of the file where we're first removed empty and commented lines and with lines sorted.

The flag --suppress-common-lines -y will display the result in two columns (-y) and only differences (--suppress-common-lines).

Once the diff is made, the command ignores the APP_KEY variable (in our example); so, yes, the expected result is:

Left side: .env                   Right side: .env.example
> CACHE_DRIVER = redis

For the illustration, we can now add a new key but just in .env (real world situation: I'm coding a new feature and I add a variable like a switch on/off)

echo 'ALLOW_FEATURE_DO_THIS = true' >> .env

Now the output will be:

Left side: .env                   Right side: .env.example
ALLOW_FEATURE_DO_THIS = true <
> CACHE_DRIVER = redis

The column on the left represents the first file (in our example .env) while the column on the right is for the second file (.env.example).

Last sample:

echo 'DATABASE_TYPE = pgsql' >> .env
echo 'DATABASE_TYPE = mysql' >> .env.example

And the result of the diff command:

Left side: .env                   Right side: .env.example
ALLOW_FEATURE_DO_THIS = true <
DATABASE_TYPE = pgsql | CACHE_DRIVER = redis
> DATABASE_TYPE = mysql

How to read:

  • ALLOW_FEATURE_DO_THIS is only present in .env,
  • DATABASE_TYPE is initialized to pgsql in .env and to mysql in .env.example,
  • CACHE_DRIVER is only present in .env.example and
  • all other lines are strictly identical (remember we've ignored commented and empty lines)