Bash Preprocessor: replace snippets with their output

Example: bake timestamp or version

#!/bin/bash

@@@START@@@
echo "# Build date: $(date)"
@@@END@@@

echo "Hello World!"

By running the preprocessor on this file, the code between @@@START@@@ and @@@END@@@ will be executed and replaced by its output.

#!/bin/bash

# Build date: Sun Jun 28 15:31:07 CEST 2020

echo "Hello World!"

Example: statically import a file

Stuff can be imported from other scripts at runtime using source, but sometimes a self-contained script is better.

#!/bin/bash

@@@START@@@
cat another-script-file.sh
@@@END@@@

echo "Hello World!"

In this case, the resulting script file will contain everything from the other script file as well.

Usage

1. Get preprocess.sh:

   • grab and extract a release
   • clone this repository
   • simply copy preprocess.sh

2. Run the script to preprocess a file (it will change its contents in place):

   ./preprocess.sh <path-to-file>
   

If needed the @@@START@@@ and @@@END@@@ tokens can be customized with an optional 2nd and 3rd argument:

./preprocess.sh <path-to-file> "<custom start token>" "<custom end token>"