In place environment variable substitution

This is a simple go module, to replace environment variables placeholders in files in place.

Example

File (at path /documents/test.txt)

Test this ${TESTA}
"${TESTB}" don't forget about this one

Having environment variables

TESTA=a
TESTB=b

After calling

inplaceenvsubst.ProcessFiles([]string{"/documents/test.txt"}, &inplaceenvsubst.Config{
    FailOnMissingVariables: false,
    RunInParallel:          false,
    ErrorListener:          nil,
})

test.txt will have the following content

Test this a
"b" don't forget about this one

Default values

You can use default values by following the following format:

${ENV:-defaultValue}

:- is considered the separator between the env key, and the default value. The default value is considered only when the env variable is not found.

Whitelist variables

You can whitelist environment variables with the WhitelistEnv value. This will ensure that all other env variables will be ignored.

inplaceenvsubst.ProcessFiles([]string{"/documents/test.txt"}, &inplaceenvsubst.Config{
    FailOnMissingVariables: false,
    RunInParallel:          false,
    ErrorListener:          nil,
    WhitelistEnvs:          inplaceenvsubst.NewStringSet("whitelisted")
})

Blacklist Variables

You can blacklist environment variables with the BlacklistEnv value. This will ensure that all other env variables will be ignored.

inplaceenvsubst.ProcessFiles([]string{"/documents/test.txt"}, &inplaceenvsubst.Config{
    FailOnMissingVariables: false,
    RunInParallel:          false,
    ErrorListener:          nil,
    BlacklistEnvs:          inplaceenvsubst.NewStringSet("blacklisted")
})

Notes

• Only accepts environment variables placeholders format ${ENV_KEY}
• $ENV_KEY will not work
• Nested env variables not supported (Ex : ${ENV_KEY ${ENV_NESTED}}, in this case, the env variable will be ENV_KEY ${ENV_NESTED})
• You cannot use both blacklists and whitelist envs