Parse a .env (dotenv) file directly using BASH

parse_dotenv.bash

# Pass the env-vars to MYCOMMAND
eval $(egrep -v '^#' .env | xargs) MYCOMMAND
# … or ...
# Export the vars in .env into your shell:
export $(egrep -v '^#' .env | xargs)

Here is my contribution, which I developed with no idea someone already did something similar (I saw too many comments and I decided to develop it instead of reading all of them):

eval "$(
    cat <(
        grep -vE -e '^\s*#' -e '^\s*$' < .env |
        grep -E "^[A-Z0-9_]+=['\"]"
    ) <(
        grep -vE -e '^\s*#' -e '^\s*$' -e "^[A-Z0-9_]+=['\"]" < .env |
        sed -r "s/^([A-Z0-9_]+=)(.*)/\\1'\\2'/"
    )
)"

Explanation:

1. Remove all comments and empty lines:
   • Regex for comments: ^\s*#
   • Regex for empty lines: ^\s*$
   • Grep command:

     grep -vE -e '^\s*#' -e '^\s*$' < .env
     

2. Get all variables that do not need treatment (i.e. those which are already inside quotes):

   grep -E "^[A-Z0-9_]+=['\"]"
   

3. Pipe step 1 to step 2:

   grep -vE -e '^\s*#' -e '^\s*$' < .env |
   grep -E "^[A-Z0-9_]+=['\"]"
   

4. Use process substitution to pass the result as a parameter to cat (I could have used a temporal file, but meh):

   <(
       grep -vE -e '^\s*#' -e '^\s*$' < .env |
       grep -E "^[A-Z0-9_]+=['\"]"
   )
   

5. Get all variables that do need treatment:

   grep -vE -e '^\s*#' -e '^\s*$' -e "^[A-Z0-9_]+=['\"]" < .env
   

   Notice how the 3 regular expressions are the same as in steps 1 and 2. The only difference here is that I reuse the -v option with the third regex.

6. Put the single quotes to avoid problems with special characters:
   • Regex for the variable with '=': ^([A-Z0-9_]+=)
   • Regex for the rest of the contents that must be inside single quotes: (.*)
   • Put the first group as is and the second between quotes: \\1'\\2'
   • Sed command:

     sed -r "s/^([A-Z0-9_]+=)(.*)/\\1'\\2'/"
     

7. Pipe step 5 to step 6:

   grep -vE -e '^\s*#' -e '^\s*$' -e "^[A-Z0-9_]+=['\"]" < .env |
   sed -r "s/^([A-Z0-9_]+=)(.*)/\\1'\\2'/"
   

8. Do pretty much the same as step 4:

   <(
       grep -vE -e '^\s*#' -e '^\s*$' -e "^[A-Z0-9_]+=['\"]" < .env |
       sed -r "s/^([A-Z0-9_]+=)(.*)/\\1'\\2'/"
   )
   

9. Concat and eval:

eval "$(
    cat <(
        grep -vE -e '^\s*#' -e '^\s*$' < .env |
        grep -E "^[A-Z0-9_]+=['\"]"
    ) <(
        grep -vE -e '^\s*#' -e '^\s*$' -e "^[A-Z0-9_]+=['\"]" < .env |
        sed -r "s/^([A-Z0-9_]+=)(.*)/\\1'\\2'/"
    )
)"

This is basically what @kolypto does here, but more complex and worse because it doesn't take into consideration the variables that contain single or double quotes inside them, because I should have been able to reuse the result of some grep commands and because maybe there is also a way to not have to feed 2 commands with the contents of the same file (I wrote < .env twice). I had some fun coding this at least ;)

If you are seeking for an aswer and have scrolled to the bottom to find it, here it is (thanks to @abij. You can see his answer here):

set -o allexport
eval $(cat '.env' | sed -e '/^#/d;/^\s*$/d' -e 's/\(\w*\)[ \t]*=[ \t]*\(.*\)/\1=\2/' -e "s/=['\"]\(.*\)['\"]/=\1/g" -e "s/'/'\\\''/g" -e "s/=\(.*\)/='\1'/g")
eval $(cat '.env.local' | sed -e '/^#/d;/^\s*$/d' -e 's/\(\w*\)[ \t]*=[ \t]*\(.*\)/\1=\2/' -e "s/=['\"]\(.*\)['\"]/=\1/g" -e "s/'/'\\\''/g" -e "s/=\(.*\)/='\1'/g")
set +o allexport

Just make sure you execute that monster in the same folder that you have your .env file.
The second eval is to read the .env.local file, whose variables should override the ones in .env

TL;DR;

local result=$(grep ^VAR_NAME=.* path/to/.env | cut -d "=" -f 2);

More protected function to get necessary var and throw error if VAR not found, or invalid path provided.

Usage:

local port=`getEnvVar --var PORT --path ./some-project/.env`;
echo "port = $port";

Code

# Throws error - if it is.
#
# @example: exitIfError $? "Your error text".
# @example: exitIfError $1 "Your error text".
function exitIfError() {
  local exit_code=$1
  shift
  [[ $exit_code ]] &&
    ((exit_code != 0)) && {
      echo "ERROR. $@" >&2;
      exit "$exit_code";
    }
}


# Gets ENV property from provided .env file
#
# @param var - Variable name
# @param path - Path to env file.
# @param [file] - Optional fileName param. @default .env.
function getEnvVar() {
  # This line is necessary to parse function named args
  # @see https://gist.github.com/mopcweb/38f5d09525f8defa5aa807d95efa8307
  while [[ $# -gt 0 ]]; do if [[ $1 == *"--"* ]]; then if [[ $2 != *"--"* ]]; then local "${1/--/}"="${2:-true}"; else local "${1/--/}"=true; fi; fi; shift; done;
  [[ -n $file ]] && local fileName=$file || local fileName=".env";

  [[ -z $var || -z $path ]] && exitIfError 1 "getEnvVar: --var & --path are required.";
  [[ ! -d $path ]] && exitIfError 1 "getEnvVar: --path should be a valid dir.";

  local result=$(grep ^$var=.* $path/$fileName | cut -d "=" -f 2);

  [[ -z $result ]] && exitIfError 1 "getEnvVar: there is no such $var var in $path/$fileName file.";

  echo $result;
}

@mopcweb Can you update with input and output, what is supported in the .env file?
And how much fun did you have, creating your own solution ;)?

# INPUT                     Expected:
'FOO=value'                 FOO='value'
"FOO=#value # comment"      FOO='#value # comment'
"FOO=value   "              FOO='value   '
'FOO='                      FOO=''
'export FOO=value'          export FOO='value'
"FOO=foo bar"               FOO='foo bar'
"FOO=   foo"                FOO='   foo'

Test cases from @ko1nksm: https://github.com/ko1nksm/shdotenv/blob/main/spec/docker_spec.sh.
Note: check his awesome script: https://github.com/ko1nksm/shdotenv !

Why not dotenv-cli?

$ dotenv <command with arguments> 
# or
$ dotenv -e .env.custom <command with arguments>

Because not every system has nodejs on it. And it's good that way.

One-liner that allows unquoted variables that contain spaces:

OLD_IFS=$IFS; IFS=$'\n'; for x in `grep -v '^#.*' .env`; do export $x; done; IFS=$OLD_IFS

ead_var() {
VAR=$(grep $1 $2 | xargs)
IFS="=" read -ra VAR <<< "$VAR"
echo ${VAR[1]}
}

MY_VAR=$(read_var MY_VAR .env)

Perfect, thanks

What about this

# save the existing environment variables
prevEnv=$(env)

# if the .env file exists, source it
[ -f .env ] && . .env

# re-export all vars from the env so they override what ever was set in .env
for e in $prevEnv
do
    export $e
done

I wrote my own because was using forbidden symbols in envs.

This basically adds apostrophes so that all variables will be treated as strings. This way you can use your Docker env files and source them with source envs.sh

import sys


def main(input_path, postfix='.sh'):
    with open(input_path, 'r') as file_handle:
        lines = file_handle.readlines()
        envs = {}
        for line in lines:
            try:
                parts = line.split('=')
                name = parts[0]
                value = ''.join(parts[1:]).rstrip('\n')
            except ValueError:
                pass
            else:
                envs[name] = value

    output_path = f'{input_path}{postfix}'
    with open(output_path, 'w') as file_handle:
        lines = []
        for name, value in envs.items():
            line = f'{name}=\'{value}\'\n'
            lines.append(line)
        file_handle.writelines(lines)


if __name__ == '__main__':
    # Passes first argument as input path.
    main(sys.argv[1])

The solution proposed by @arizonaherbaltea will not work correctly when the file is not terminated with a newline. For example using this .env example,

# test.env
MY_VAR=a

Will not work properly, whereas the following will,

# test.env
MY_VAR=a

The only change is adding a newline at the end of the file. This is because read requires a newline to parse the line correctly. Thus, in order to ensure everything works properly we can add a check to see if the file ends with newline and if not append it before parsing it. Doing this will ensure all lines are parsed correctly.

#!/bin/bash

function export_envs() {
  local env_file=${1:-.env}
  local is_comment='^[[:space:]]*#'
  local is_blank='^[[:space:]]*$'
  echo "trying env file: ${env_file}"

  # ensure it has a newline that the end, if it does not already
  tail_line=`tail -n 1 "${env_file}"`
  if [[ "${tail_line}" != "" ]]; then
      echo "No Newline at end of ${env_file}, appending!"
      echo "" >> "${env_file}"
  fi

  while IFS= read -r line; do
    echo "${line}"
    [[ $line =~ $is_comment ]] && continue
    [[ $line =~ $is_blank ]] && continue
    key=$(echo "$line" | cut -d '=' -f 1)
    # shellcheck disable=SC2034
    value=$(echo "$line" | cut -d '=' -f 2-)
    # shellcheck disable=SC2116,SC1083
    echo "The key: ${key} and value: ${value}"
    eval "export ${key}=\"$(echo \${value})\""
  done < <(cat "${env_file}")
}

export_envs ${1}

Then it results,

✗ ./test.sh test.env
trying env file: test.env
The key: MY_VAR and value: a
The key: MY_VAR and value: b

Hope this helps someone out there :)

I've been using shdotenv from @ko1nksm and it's been great.

You can do shdotenv my-command to parse and run a command.
If you want to export the variables to the shell session, use eval $(shdotenv).

What's wrong with:

if [ -f .env ]; then
    set -o allexport
    source .env
fi

Works on macOS with my .env that works with docker compose and does not have quotes around every string.

Test with:

envsubst < "$secret_file" | cat

later in the same script.

@tgrushka's method is the most reliable one for me when used in scripts.

You can also use it like this if your env vars are in a string:

set -o allexport
source <(grep -Ev '^#' <<< "$YOUR_ENV_VAR_STRING")
# rest of the script