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Automatic replace variables in configuration file templates from environment variables.

The parameters program takes an input file template and a given regular expression for searching environment variables. The variables in the template file will be replaced by the values of found environment variables by the exact same name.


Simple example

First set the environment variables. This can also come from GitLab CI variables:

export SYMF_DB_USER=my_user
export SYMF_DB_PASS=my_super_secret_password

Then set up a dotenv template file (.env.dist):


Now parameters will replace the variables:

$ parameters --input .env.dist --regexp ^SYMF_ > .env

This will take .env.dist as input file and ^SYMF_ as regular expression to search for variables in your shell environment. Searching the environment variables by a given regular expression is the same as running env | grep ^SYMF_ in your shell.

The result in .env file:


Example using different envrionments

You can also use different environments like Testing, Staging, Production, etc.

$ parameters --input .env.dist --regexp ^SYMF_ --env testing > .env

testing will be converted to TESTING.

Example using different instances

$ parameters --input .env.dist --regexp ^SYMF_ --instance shopa > .env

shopa will be converted to SHOPA.

Also a combination is possible.

$ parameters --input .env.dist --regexp ^SYMF_ --env testing --instance shopa > .env

Run parameters --help to see more parameters.


  • CMake (For building)
  • Boost (Filesystem / Program Options)

Optional Dependencies

Install dependencies on macOS

$ brew install boost

Install dependencies on Debian 9

$ sudo apt-get install --no-install-recommends libboost-filesystem-dev libboost-program-options-dev

Build from Source

You need a modern C++ compiler that supports C++14 and CMake 3.8 or later.

This will build the binary:

$ ./bin/

Then the binary is available in build_release/bin.

After building the project, run:

$ ./bin/

Install via Debian repository

Only Debian 9 (stretch) is supported.

Add the public GPG key to the apt sources keyring:

$ wget -qO - '' | sudo apt-key add -

Verify key on the keyring. This should print out informations about the key:

$ apt-key list

Add apt source file and update:

$ echo "deb stretch main" > /etc/apt/sources.list.d/fox21at.list
$ apt-get update

Install the package:

$ sudo apt-get install parameters

Now you can run the program:

$ parameters --help

Install under Debian via .deb file

Go to the GitHub releases page and download the desired version file. Then run:

$ sudo dpkg --install parameters.deb

Install via Homebrew

  1. Add the thefox/brewery tap to brew.

    $ brew tap thefox/brewery
  2. Actual installation

    $ brew install parameters

Tested under

  • macOS 10.13 High Sierra
  • macOS 10.14 Mojave
  • Debian 8 (jessie)
  • Debian 9 (stretch)


Copyright (C) 2018 Christian Mayer

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see