substenv

A wrapper bash script which add some extra features like interactivity to envsubst utility.

Get Started

Under the hood, substenv uses envsubst utility to substitute the values of environment variables in the standard input content.

This is a standanlone script. Hence it will be executed out of the box in a bash environment, provided you have envsubst and gnu-getopt utilities in your PATH.

Download envsubst.sh and move it to your suited your location.
Execute it from a terminal running Bash just like you would with envsubst

cd path/to/substenv
./substenv.sh < /path/to/input_file > /path/to/output_file

How it works

In normal operation mode, standard input is copied to standard output, with references to environment variables of the form $VARIABLE or ${VARIABLE} being replaced with the corresponding values. If a SHELL-FORMAT is given, only those environment variables that are referenced in SHELL-FORMAT are substituted; otherwise all environment variables references occurring in standard input are substituted.

When --variables is used, the output consists of the environment variables that are referenced either in SHELL-FORMAT if provided or in standard input, one per line.

Usage

substenv.sh [OPTIONS] [SHELL-FORMAT]
                [-h|--help] [-V|--version] [-v|--variables] [-i|--interactive] [SHELL-FORMAT]
                [-i|--interactive] [SHELL-FORMAT]
                [-v|--variables] [SHELL-FORMAT]
                [-h|--help]
                [-V|--version]

Options

Operation mode :

-i, --interactive

Prompt for a value for each variable discovered in the standard input, prior to performing substitution. Cannot be used in conjonction with -v or --variable switch

-v, --variables

Output the variables occurring in SHELL-FORMAT or in the input content, if any. Cannot be used in conjonction with -i or --interactive switch.

Informative output :

-h, --help

display this help and exit

-V, --version

output version information and exit

License